Evidence for metallization in dense oxygen has been reported for over 30 years[Desgreniers et al.,J.Phys.Chem.94,1117(1990)]at a now routinely accessible 95 GPa[Shimizu et al.,Nature 393,767(1998)].However,despite the...Evidence for metallization in dense oxygen has been reported for over 30 years[Desgreniers et al.,J.Phys.Chem.94,1117(1990)]at a now routinely accessible 95 GPa[Shimizu et al.,Nature 393,767(1998)].However,despite the longevity of this result and the technological advances since,the nature of the metallic phase remains poorly constrained[Akahama et al.,Phys.Rev.Lett.74,4690(1995);Goncharov et al.,Phys.Rev.B 68,224108(2003);Ma,Phys.Rev.B 76,064101(2007);and Weck et al.,Phys.Rev.Lett.102,255503(2009)].In this work,through Raman spectroscopy,we report the distinct vibrational characteristics of metallicζ-O_(2) from 85 to 225 GPa.In comparison with numerical simulations,wefind reasonable agreement with the candidate structure up to about 150 GPa.At higher pressures,the C2/mstructure is found to be unstable and incompatible with experimental observations.Alternative candidate structures,and Ci,with C2/m C2/conly two molecules in the primitive unit cell,are found to be stable and more compatible with measurements above 175 GPa,indicative of the dissociation of(O_(2))4 units.Further,we report and discuss a strong hysteresis and metastability with the precursory phaseϵ-O_(2).Thesefindings will reinvigorate experimental and theoretical work into the dense oxygen system,which will have importance for oxygen-bearing chemistry,prevalent in the deep Earth,as well as fundamental physics.展开更多
Important challenges must be addressed to make wind turbines sustainable renewable energy sources.A typical problem concerns the design of the foundation.If the pile diameter is larger than that of the jacket platform...Important challenges must be addressed to make wind turbines sustainable renewable energy sources.A typical problem concerns the design of the foundation.If the pile diameter is larger than that of the jacket platform,traditional mechanical models cannot be used.In this study,relying on the seabed soil data of an offshore wind farm,the m-method and the equivalent embedded method are used to address the single-pile wind turbine foundation problem for different pile diameters.An approach to determine the equivalent pile length is also proposed accordingly.The results provide evidence for the effectiveness and reliability of the model based on the equivalent embedded method.展开更多
Changes in the concentration of charged ions in neurons can generate induced electric fields,which can further modulate cell membrane potential.In this paper,Fourier coefficients are used to investigate the effect of ...Changes in the concentration of charged ions in neurons can generate induced electric fields,which can further modulate cell membrane potential.In this paper,Fourier coefficients are used to investigate the effect of electric field on vibrational resonance for signal detection in a single neuron model and a bidirectionally coupled neuron model,respectively.The study found that the internal electric field weakens vibrational resonance by changing two factors,membrane potential and phase-locked mode,while the periodic external electric field of an appropriate frequency significantly enhances the vibrational resonance,suggesting that the external electric field may play a constructive role in the detection of weak signals in the brain and neuronal systems.Furthermore,when the coupling of two neurons is considered,the effect of the electric field on the vibrational resonance is similar to that of a single neuron.The paper also illustrates the effect of electric field coupling on vibrational resonance.This study may provide a new theoretical basis for understanding information encoding and transmission in neurons.展开更多
Effects of system size,coupling strength,and noise on vibrational resonance(VR)of globally coupled bistable systems are investigated.The power spectral amplifications obtained by the three methods all show that the VR...Effects of system size,coupling strength,and noise on vibrational resonance(VR)of globally coupled bistable systems are investigated.The power spectral amplifications obtained by the three methods all show that the VR exists over a wide range of parameter values.The increase in system size induces and enhances the VR,while the increase in noise intensity suppresses and eventually eliminates the VR.Both the stochastic resonance and the system size resonance can coexist with the VR in different parameter regions.This research has potential applications to the weak signal detection process in stochastic multi-body systems.展开更多
The vibrational motions are usually neglected when calculating(e,2e) triple differential cross sections(TDCSs) of molecules. Here, multi-center distorted-wave method(MCDW) has been modified by including molecular vibr...The vibrational motions are usually neglected when calculating(e,2e) triple differential cross sections(TDCSs) of molecules. Here, multi-center distorted-wave method(MCDW) has been modified by including molecular vibrations. This vibrational MCDW method is employed to calculate the TDCSs of 1b3gorbital of ethylene at low(100 eV) and medium(250 eV) incident electron energies in coplanar asymmetric kinematic condition. The results show that molecular vibrations significantly influence the angular distributions of the TDCSs, especially in the binary region along momentum transfer near the Bethe ridge.展开更多
The application of vibrational spectroscopy in the pharmaceutical industry is widely investigated, from the quality assurance of the product during the production process control to the final products’ quality contro...The application of vibrational spectroscopy in the pharmaceutical industry is widely investigated, from the quality assurance of the product during the production process control to the final products’ quality control and the authentication of products on the markets. This study focuses on non-contact and noninvasive detection and identification of pain-relievers at 1-5 meters standoff distances. The specimens analyzed include standard laboratory-grade active ingredients and commercially available pain relievers in powder, solid and liquid forms. All the remote measurements captured revealed the Raman signatures of the specimens, with varying peak intensities. To correlate the band intensities captured with the standoff distances between the laser source and the specimens, the intensity ratios of the two prominent peaks of the laboratory grade reference active ingredient (1607 and 1319 cm<sup>-1</sup>) normalized with 1319 cm<sup>-1</sup> are used. The results of the study suggest the viability of standoff Raman spectroscopy for routine monitoring and identification of pharma-ceuticals, including counterfeit pain relievers.展开更多
Decoupling the complicated vibrational-vibrational (V-V) coupling of a multimode vibrational relaxation remains a challenge for analyzing the sound relaxational absorption in multi-component gas mixtures. In our pre...Decoupling the complicated vibrational-vibrational (V-V) coupling of a multimode vibrational relaxation remains a challenge for analyzing the sound relaxational absorption in multi-component gas mixtures. In our previous work [Acta Phys. Sin. 61 174301 (2012)], an analytical model to predict the sound absorption from vibrational relaxation in a gas medium is proposed. In this paper, we develop the model to decouple the V-V coupled energy to each vibrationaltranslational deexcitation path, and analyze how the multimode relaxations form the peaks of sound absorption spectra in gas mixtures. We prove that a multimode relaxation is the sum of its decoupled single-relaxation processes, and only the decoupled process with a significant isochoric-molar-heat can be observed as an absorption peak. The decoupling model clarifies the essential processes behind the peaks in spectra arising from the multimode relaxations in multi-component gas mixtures. The simulation validates the proposed decoupling model.展开更多
Characterization of real-time and ultrafast motions of the complex molecules at surface and interface is critical to understand how interracial molecules function. It requires to develop surface-sensitive, fast-identi...Characterization of real-time and ultrafast motions of the complex molecules at surface and interface is critical to understand how interracial molecules function. It requires to develop surface-sensitive, fast-identification, and time-resolved techniques. In this study, we employ several key technical procedures and successfully develop a highly sensitive femtosecond time-resolved sum frequency generation vibrational spectroscopy (SFG-VS) system. This system is able to measure the spectra with two polarization combinations (ssp and ppp, or psp and ssp) simultaneously. It takes less than several seconds to collect one spectrum. To the best of our knowledge, it is the fastest speed of collecting SFG spectra reported by now. Using the time-resolved measurement, ultrafast vibrational dynamics of the N-H mode of α-helical peptide at water interface is determined. It is found that the membrane environment does not affect the N-H vibrational relaxation dynamics. It is expected that the time-resolved SFG system will play a vital role in the deep understanding of the dynamics and interaction of the complex molecules at surface and interface. Our method may also provide an important technical proposal for the people who plan to develop time-resolved SFG systems with simultaneous measurement of multiple polarization combinations.展开更多
Based on previous laser-induced fluorescence excitation spectroscopy work, the vibrational constants of neutral FeS in the X5 △ electronic state were obtained by directly mapping the ground-state vibrational levels u...Based on previous laser-induced fluorescence excitation spectroscopy work, the vibrational constants of neutral FeS in the X5 △ electronic state were obtained by directly mapping the ground-state vibrational levels up to v"=3 using conventional laser-induced dispersed fluorescence spectroscopy. The vibrational frequency of FeS(X5 △) (518±5 cm-1) agrees well with that reported in a recent PES measurement (520±30 cm-1) [J. Phys. Chem. A 107, 2821 (2003)] which is the only one prior experimental vibrational frequency value for the 5 △ state of FeS. Careful comparisons of our experimental results and those documented in the literature (mainly from theoretical predictions) suggest that the ground state of FeS is 5 △ state.展开更多
An algebraic Harniltonian for the two coupled nonlinear vibrations of highly excited nonrigid molecule HCP was presented. The Hamiltonian reduces to the conventional one in a limit which was expressed in terms of harm...An algebraic Harniltonian for the two coupled nonlinear vibrations of highly excited nonrigid molecule HCP was presented. The Hamiltonian reduces to the conventional one in a limit which was expressed in terms of harmonic oscillator operators. It showed that the algebraic model can better reproduce the data than the conventional model by fitting the observed data of HCP.展开更多
The potential energy curves of the ground state X2∑+g of the fluorine molecule have been accurately reconstructed employing the Ryderg-Klein-Rees (RKR) method extrapolated by a Hulburt and Hirschfeler potential fu...The potential energy curves of the ground state X2∑+g of the fluorine molecule have been accurately reconstructed employing the Ryderg-Klein-Rees (RKR) method extrapolated by a Hulburt and Hirschfeler potential function for longer internuclear distances. Solving the corresponding radial one-dimensional Schr?dinger equation of nuclear motion yields 22 bound vibrational levels above v=0. The comparison of these theoretical levels with the experimental data yields a mean absolute deviation of about 7.6 cm^-1 over the 23 levels. The highest vibrational level energy obtained using this method is 13308.16 cm?1 and the relative deviation compared with the experimental datum of 13408.49 cm^-1 is only 0.74%. The value from our method is much closer and more accurate than the value obtained by the quantum mechanical ab initio method by Bytautas. The reported agreement of the vibrational levels and dissociation energy with experiment is contingent upon the potential energy curve of the F2 ground state.展开更多
In this paper, we have applied the Lie algebraic model to nano-bio molecules to determine the vibrational spectra of different stretching and bending vibrational modes. The determined vibrational energy levels by the ...In this paper, we have applied the Lie algebraic model to nano-bio molecules to determine the vibrational spectra of different stretching and bending vibrational modes. The determined vibrational energy levels by the Lie algebraic model are compared with the experimental data. The results from the theoretical mode[ are consistent with the experimental data. The vibrational energy levels are clustering in the excited states.展开更多
The vibrational wave function of the target theoretically plays an important role in the calculation of vibrational excitation cross sections. By a careful study of the differential cross sections resulting from diffe...The vibrational wave function of the target theoretically plays an important role in the calculation of vibrational excitation cross sections. By a careful study of the differential cross sections resulting from different vibrational wave functions we find that cross sections are susceptible to vibrational wave functions. Minor changes in the vibration wave lhnction may cause a significant change in the cross section. Even more surprising is that by selecting a few numbers of potential models (which determine the vibrational wave functions) we can often calculate the differential scattering cross section in much closer agreement with experiment in the framework of body-frame vibrational close-coupling theory, which suggest that an accurate potential energy may play a more important role in scattering than we thought betbre.展开更多
An improved U(2) algebraic model is introduced to study the stretching and bending vibrational spectra of methane and its isotopomers.The algebraic model with fewer parameters reproduces the experimental spectra wit...An improved U(2) algebraic model is introduced to study the stretching and bending vibrational spectra of methane and its isotopomers.The algebraic model with fewer parameters reproduces the experimental spectra with good precision.Moreover,the obtained parameters describe well the correct behavior of isotopic substitution.It is shown that the Fermi resonance leads to a very fast intramolecular vibrational redistribution among stretches and bends.展开更多
Ba[(Zn_(1-x)Mg_x)_(1/3)Ta(2/3)]O_3(BZMT,x=0,0.2,0.4,0.6,0.8,and 1.0)solid solution ceramics were synthesized by a conventional solid-state sintering technique.Vibration spectra(Raman spectroscopy and Fourier trans for...Ba[(Zn_(1-x)Mg_x)_(1/3)Ta(2/3)]O_3(BZMT,x=0,0.2,0.4,0.6,0.8,and 1.0)solid solution ceramics were synthesized by a conventional solid-state sintering technique.Vibration spectra(Raman spectroscopy and Fourier trans form far-infrared reflection spectroscopy)and X-ray diffraction(XRD)were employed to evaluate the correla tion between microstructures and phonon modes of these solid solutions.Spectroscopic and structural data show sensitivity to structural evolution of samples with Mg^(2+)concentration,and a 1:2 ordered phase appears when x≥0.2.The unit cell parameters decrease with increasing Mg^(2+)content.The ordering degree reaches a relative maximum value in the range of Mg^(2+)content,0.4≤x<0.6.The phonon modes were assigned,and the correlation of phonon vibrations in the microstructure were analyzed.The position and width of the phonon modes were determined and correlated to the ionic radii for the different atoms substituted in the B'-site.展开更多
Cell membranes play a crucial role in many biological functions of cells. A small change in the composition of cell membranes can strongly influence the functions of membrane-associated proteins, such as ion and water...Cell membranes play a crucial role in many biological functions of cells. A small change in the composition of cell membranes can strongly influence the functions of membrane-associated proteins, such as ion and water channels, and thus mediate the chemical and physical balance in cells. Such composition change could originate from the introduction of short-chain alcohols, or other anesthetics into membranes. In this work, we have applied sum frequency generation vibrational spectroscopy (SFG-VS), supplemented by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), to investigate interaction between methanol and 1,2-dimyristoyl-d54-sn-glycero-3-phosphocholine (d54-DMPC) lipid bilayers. Lipid's hydrocarbon interior is deuterated while its head group is hydrogenated. At the same time, CH3 symmetric stretch from methanol and lipid head amine group has different frequency, thus we can distinguish the behaviors of methanol, lipid head amine group, and lipid hydrocarbon interior. Based on the spectral feature of the bending mode of the water molecules replaced by methanol, we determined that the methanol molecules are intercalated into the region between amine and phosphate groups at the lipid hydrophilic head. The dipole of CH3 groups of methanol and lipid head, and the water O-H M1 adopt the same orientation directions. The introduction of methanol into the lipid hydrophilic head group can strongly perturb the entire length of the alkyl chains, resulting that the signals of CD2 and CD3 groups from both leaflets can not cancel each other.展开更多
Four-, six-, and eight-membered ring silica nanotubes at temperatures from 300 K to 1600 K are relaxed by classical molecular dynamics simulations with three potential models. The simulation results indicate that the ...Four-, six-, and eight-membered ring silica nanotubes at temperatures from 300 K to 1600 K are relaxed by classical molecular dynamics simulations with three potential models. The simulation results indicate that the stability of the end rings of the three silica nanotubes gradually decreases with increase in temperature. The validity of the vibrational features of silica nanotubes is shown by the vibrational density of states. Infrared spectra on the silica nanotubes under different temperatures are investigated. A detailed assignment of each spectral peak to the corresponding vibrational mode of the three nanotubes has been addressed. The results are in good agreement with the other theoretical and experimental展开更多
Sum frequency generation vibrational spectroscopy (SFG-VS) is a robust technique for inter- facial investigation at molecular level. The performance of SFG-VS mostly depends on the spectral resolution of the SFG sys...Sum frequency generation vibrational spectroscopy (SFG-VS) is a robust technique for inter- facial investigation at molecular level. The performance of SFG-VS mostly depends on the spectral resolution of the SFG system. In this research, a simplified function was deduced to calculate the spectral resolution of picosecond SFG system and the lineshape of SFG spectra based on the Guassian shaped functions of IR beam and visible beam. The function indicates that the lineshpe of SFG spectra from nonresonant samples can be calculated by the Guassian widths of both IR beam and visible beam. And the Voigt lineshape of SFG spectra from vibrational resonant samples can be calculated by the Homogeneous broadening (Lorentzian width) and Inhomogeneous broadening (Guassian width) of vibrational modes, as well as the Guassian widths of both IR beam and visible beam. Such functions were also applied to verify the spectral resolution of the polarization-resolved and frequency-resolved picosecond SFG-VS system which was developed by our group recently. It is shown that the linewidths of IR beams that generated from current laser system are about 1.5 cm-1. The calculated spectral resolution of current picosecond IR scanning SFG-VS system is about 4.6 cm-1, which is consist with he spctral resolution shown in the spectra of cholesterol monolayer (3.5-5 cm-1).展开更多
On the basis of the records of strong seismic events taking place in soft carbonate sediments, a new seismic sequence system of vibrational liquefaction is established, which consists of a series of units, such as esc...On the basis of the records of strong seismic events taking place in soft carbonate sediments, a new seismic sequence system of vibrational liquefaction is established, which consists of a series of units, such as escaped structure of micrite veins and liquefied deformation formed in the period of seismic liquefaction, land subsidence structure after liquefaction, tsunamic hummocky and turbidite produced by seismic events, This sequence is a generalization and summation of field observation in vast areas, which shows the whole process of a strong seismic event and provides an unified theoretical explanation. The pattern of the seismic sequence by vibrational liquefaction provides one of correlation standards for geologists in the field to discriminate events in carbonate sequences. Based on the pattern of seismic sequence, the authors first advance a new conception of the Palaeo-Tanlu (Tancheng-Lujiang) Zone and discuss primarily its geological significations.展开更多
Resonant and nonresonant intermolecular vibrational energy transfers in Gdm- SCN/KSCN=1/1, GdmSCN/KS^13CN=1/1 and GdmSCN/KS^13C^15N=1/1 mixed crystals in melts and in aqueous solutions are studied with the two dimensi...Resonant and nonresonant intermolecular vibrational energy transfers in Gdm- SCN/KSCN=1/1, GdmSCN/KS^13CN=1/1 and GdmSCN/KS^13C^15N=1/1 mixed crystals in melts and in aqueous solutions are studied with the two dimensional infrared spectroscopy. The energy transfers in the samples are slower with a larger energy donor/acceptor gap, independent of the Raman spectra. The energy gap dependences of the nonresonant energy transfers cannot be described by the phonon compensation mechanism. Instead, the experi- mental energy gap dependences can be quantitatively described by the dephasing mechanism. Temperature dependences of resonant and nonresonant energy transfer rates in the melts are also consistent with the prediction of the dephasing mechanism. The series of results suggest that the dephasing mechanism can be dominant not only in solutions, but also in melts (pure liquids without solvents), only if the molecular motions (translations and rotations) are much faster than the nonresonant energy transfer processes.展开更多
基金The computational resources were provided by the Cambridge Tier-2 sys-tem operated by the University of Cambridge Research Computing Service and funded by the UK EPSRC(Grant No.EP/P020259/1).
文摘Evidence for metallization in dense oxygen has been reported for over 30 years[Desgreniers et al.,J.Phys.Chem.94,1117(1990)]at a now routinely accessible 95 GPa[Shimizu et al.,Nature 393,767(1998)].However,despite the longevity of this result and the technological advances since,the nature of the metallic phase remains poorly constrained[Akahama et al.,Phys.Rev.Lett.74,4690(1995);Goncharov et al.,Phys.Rev.B 68,224108(2003);Ma,Phys.Rev.B 76,064101(2007);and Weck et al.,Phys.Rev.Lett.102,255503(2009)].In this work,through Raman spectroscopy,we report the distinct vibrational characteristics of metallicζ-O_(2) from 85 to 225 GPa.In comparison with numerical simulations,wefind reasonable agreement with the candidate structure up to about 150 GPa.At higher pressures,the C2/mstructure is found to be unstable and incompatible with experimental observations.Alternative candidate structures,and Ci,with C2/m C2/conly two molecules in the primitive unit cell,are found to be stable and more compatible with measurements above 175 GPa,indicative of the dissociation of(O_(2))4 units.Further,we report and discuss a strong hysteresis and metastability with the precursory phaseϵ-O_(2).Thesefindings will reinvigorate experimental and theoretical work into the dense oxygen system,which will have importance for oxygen-bearing chemistry,prevalent in the deep Earth,as well as fundamental physics.
基金supported by the National Natural Science Foundation of China (52071055)the Fundamental Research Funds for the Central Universities (Grant No.DUT22QN237).
文摘Important challenges must be addressed to make wind turbines sustainable renewable energy sources.A typical problem concerns the design of the foundation.If the pile diameter is larger than that of the jacket platform,traditional mechanical models cannot be used.In this study,relying on the seabed soil data of an offshore wind farm,the m-method and the equivalent embedded method are used to address the single-pile wind turbine foundation problem for different pile diameters.An approach to determine the equivalent pile length is also proposed accordingly.The results provide evidence for the effectiveness and reliability of the model based on the equivalent embedded method.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51737003 and 51977060)the Natural Science Foundation of Hebei Province,China(Grant No.E2011202051)。
文摘Changes in the concentration of charged ions in neurons can generate induced electric fields,which can further modulate cell membrane potential.In this paper,Fourier coefficients are used to investigate the effect of electric field on vibrational resonance for signal detection in a single neuron model and a bidirectionally coupled neuron model,respectively.The study found that the internal electric field weakens vibrational resonance by changing two factors,membrane potential and phase-locked mode,while the periodic external electric field of an appropriate frequency significantly enhances the vibrational resonance,suggesting that the external electric field may play a constructive role in the detection of weak signals in the brain and neuronal systems.Furthermore,when the coupling of two neurons is considered,the effect of the electric field on the vibrational resonance is similar to that of a single neuron.The paper also illustrates the effect of electric field coupling on vibrational resonance.This study may provide a new theoretical basis for understanding information encoding and transmission in neurons.
基金Project supported by the Xing Dian Talents Support Project of Yunnan Province(Grant No.YNWR-QNBJ-2018-0040)the Youth Project of Applied Basic Research of Yunnan Science(Grant No.202201AU070062)the Yunnan University’s Research Innovation Fund for Graduate Students(Grant No.KC-22221171).
文摘Effects of system size,coupling strength,and noise on vibrational resonance(VR)of globally coupled bistable systems are investigated.The power spectral amplifications obtained by the three methods all show that the VR exists over a wide range of parameter values.The increase in system size induces and enhances the VR,while the increase in noise intensity suppresses and eventually eliminates the VR.Both the stochastic resonance and the system size resonance can coexist with the VR in different parameter regions.This research has potential applications to the weak signal detection process in stochastic multi-body systems.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 12004370 and 12127804)the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB34020000)。
文摘The vibrational motions are usually neglected when calculating(e,2e) triple differential cross sections(TDCSs) of molecules. Here, multi-center distorted-wave method(MCDW) has been modified by including molecular vibrations. This vibrational MCDW method is employed to calculate the TDCSs of 1b3gorbital of ethylene at low(100 eV) and medium(250 eV) incident electron energies in coplanar asymmetric kinematic condition. The results show that molecular vibrations significantly influence the angular distributions of the TDCSs, especially in the binary region along momentum transfer near the Bethe ridge.
文摘The application of vibrational spectroscopy in the pharmaceutical industry is widely investigated, from the quality assurance of the product during the production process control to the final products’ quality control and the authentication of products on the markets. This study focuses on non-contact and noninvasive detection and identification of pain-relievers at 1-5 meters standoff distances. The specimens analyzed include standard laboratory-grade active ingredients and commercially available pain relievers in powder, solid and liquid forms. All the remote measurements captured revealed the Raman signatures of the specimens, with varying peak intensities. To correlate the band intensities captured with the standoff distances between the laser source and the specimens, the intensity ratios of the two prominent peaks of the laboratory grade reference active ingredient (1607 and 1319 cm<sup>-1</sup>) normalized with 1319 cm<sup>-1</sup> are used. The results of the study suggest the viability of standoff Raman spectroscopy for routine monitoring and identification of pharma-ceuticals, including counterfeit pain relievers.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 60971009 and 61001011)the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20090142110019)+1 种基金the Natural Science Foundation of Hubei Province, China (Grant No. 2010CDB02701)the Fundamental Research Funds for the Central Universities, China (Grant No. 2012QN083)
文摘Decoupling the complicated vibrational-vibrational (V-V) coupling of a multimode vibrational relaxation remains a challenge for analyzing the sound relaxational absorption in multi-component gas mixtures. In our previous work [Acta Phys. Sin. 61 174301 (2012)], an analytical model to predict the sound absorption from vibrational relaxation in a gas medium is proposed. In this paper, we develop the model to decouple the V-V coupled energy to each vibrationaltranslational deexcitation path, and analyze how the multimode relaxations form the peaks of sound absorption spectra in gas mixtures. We prove that a multimode relaxation is the sum of its decoupled single-relaxation processes, and only the decoupled process with a significant isochoric-molar-heat can be observed as an absorption peak. The decoupling model clarifies the essential processes behind the peaks in spectra arising from the multimode relaxations in multi-component gas mixtures. The simulation validates the proposed decoupling model.
文摘Characterization of real-time and ultrafast motions of the complex molecules at surface and interface is critical to understand how interracial molecules function. It requires to develop surface-sensitive, fast-identification, and time-resolved techniques. In this study, we employ several key technical procedures and successfully develop a highly sensitive femtosecond time-resolved sum frequency generation vibrational spectroscopy (SFG-VS) system. This system is able to measure the spectra with two polarization combinations (ssp and ppp, or psp and ssp) simultaneously. It takes less than several seconds to collect one spectrum. To the best of our knowledge, it is the fastest speed of collecting SFG spectra reported by now. Using the time-resolved measurement, ultrafast vibrational dynamics of the N-H mode of α-helical peptide at water interface is determined. It is found that the membrane environment does not affect the N-H vibrational relaxation dynamics. It is expected that the time-resolved SFG system will play a vital role in the deep understanding of the dynamics and interaction of the complex molecules at surface and interface. Our method may also provide an important technical proposal for the people who plan to develop time-resolved SFG systems with simultaneous measurement of multiple polarization combinations.
基金Acknowledgment: This work was supported by the National Natural Science Foundation of China (No.20673107 and No.20873133), the National Basic Research Program of China (No.2007CB815203 and No.2010CB923302), the Chinese Academy of Sciences (No.KJCX2-YW-N24), and the Scientific Research Foundation for the Returned Overseas Chinese Scholars, Ministry of Education of China.
文摘Based on previous laser-induced fluorescence excitation spectroscopy work, the vibrational constants of neutral FeS in the X5 △ electronic state were obtained by directly mapping the ground-state vibrational levels up to v"=3 using conventional laser-induced dispersed fluorescence spectroscopy. The vibrational frequency of FeS(X5 △) (518±5 cm-1) agrees well with that reported in a recent PES measurement (520±30 cm-1) [J. Phys. Chem. A 107, 2821 (2003)] which is the only one prior experimental vibrational frequency value for the 5 △ state of FeS. Careful comparisons of our experimental results and those documented in the literature (mainly from theoretical predictions) suggest that the ground state of FeS is 5 △ state.
文摘An algebraic Harniltonian for the two coupled nonlinear vibrations of highly excited nonrigid molecule HCP was presented. The Hamiltonian reduces to the conventional one in a limit which was expressed in terms of harmonic oscillator operators. It showed that the algebraic model can better reproduce the data than the conventional model by fitting the observed data of HCP.
基金This work was supported by the National Natural Science Foundation of China (No.20273066).
文摘The potential energy curves of the ground state X2∑+g of the fluorine molecule have been accurately reconstructed employing the Ryderg-Klein-Rees (RKR) method extrapolated by a Hulburt and Hirschfeler potential function for longer internuclear distances. Solving the corresponding radial one-dimensional Schr?dinger equation of nuclear motion yields 22 bound vibrational levels above v=0. The comparison of these theoretical levels with the experimental data yields a mean absolute deviation of about 7.6 cm^-1 over the 23 levels. The highest vibrational level energy obtained using this method is 13308.16 cm?1 and the relative deviation compared with the experimental datum of 13408.49 cm^-1 is only 0.74%. The value from our method is much closer and more accurate than the value obtained by the quantum mechanical ab initio method by Bytautas. The reported agreement of the vibrational levels and dissociation energy with experiment is contingent upon the potential energy curve of the F2 ground state.
文摘In this paper, we have applied the Lie algebraic model to nano-bio molecules to determine the vibrational spectra of different stretching and bending vibrational modes. The determined vibrational energy levels by the Lie algebraic model are compared with the experimental data. The results from the theoretical mode[ are consistent with the experimental data. The vibrational energy levels are clustering in the excited states.
基金supported by the National Natural Science Foundation of China(Grant No.11647058)the Fund for Sichuan Distinguished Scientists(Grant No.2015JQ0042)the Youth Innovation Team of the Education Department of Sichuan Province,China(Grant No.14TD0013)
文摘The vibrational wave function of the target theoretically plays an important role in the calculation of vibrational excitation cross sections. By a careful study of the differential cross sections resulting from different vibrational wave functions we find that cross sections are susceptible to vibrational wave functions. Minor changes in the vibration wave lhnction may cause a significant change in the cross section. Even more surprising is that by selecting a few numbers of potential models (which determine the vibrational wave functions) we can often calculate the differential scattering cross section in much closer agreement with experiment in the framework of body-frame vibrational close-coupling theory, which suggest that an accurate potential energy may play a more important role in scattering than we thought betbre.
基金Project supported by the National Natural Science Foundation of China (Grant No. 11174099)
文摘An improved U(2) algebraic model is introduced to study the stretching and bending vibrational spectra of methane and its isotopomers.The algebraic model with fewer parameters reproduces the experimental spectra with good precision.Moreover,the obtained parameters describe well the correct behavior of isotopic substitution.It is shown that the Fermi resonance leads to a very fast intramolecular vibrational redistribution among stretches and bends.
文摘Ba[(Zn_(1-x)Mg_x)_(1/3)Ta(2/3)]O_3(BZMT,x=0,0.2,0.4,0.6,0.8,and 1.0)solid solution ceramics were synthesized by a conventional solid-state sintering technique.Vibration spectra(Raman spectroscopy and Fourier trans form far-infrared reflection spectroscopy)and X-ray diffraction(XRD)were employed to evaluate the correla tion between microstructures and phonon modes of these solid solutions.Spectroscopic and structural data show sensitivity to structural evolution of samples with Mg^(2+)concentration,and a 1:2 ordered phase appears when x≥0.2.The unit cell parameters decrease with increasing Mg^(2+)content.The ordering degree reaches a relative maximum value in the range of Mg^(2+)content,0.4≤x<0.6.The phonon modes were assigned,and the correlation of phonon vibrations in the microstructure were analyzed.The position and width of the phonon modes were determined and correlated to the ionic radii for the different atoms substituted in the B'-site.
文摘Cell membranes play a crucial role in many biological functions of cells. A small change in the composition of cell membranes can strongly influence the functions of membrane-associated proteins, such as ion and water channels, and thus mediate the chemical and physical balance in cells. Such composition change could originate from the introduction of short-chain alcohols, or other anesthetics into membranes. In this work, we have applied sum frequency generation vibrational spectroscopy (SFG-VS), supplemented by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), to investigate interaction between methanol and 1,2-dimyristoyl-d54-sn-glycero-3-phosphocholine (d54-DMPC) lipid bilayers. Lipid's hydrocarbon interior is deuterated while its head group is hydrogenated. At the same time, CH3 symmetric stretch from methanol and lipid head amine group has different frequency, thus we can distinguish the behaviors of methanol, lipid head amine group, and lipid hydrocarbon interior. Based on the spectral feature of the bending mode of the water molecules replaced by methanol, we determined that the methanol molecules are intercalated into the region between amine and phosphate groups at the lipid hydrophilic head. The dipole of CH3 groups of methanol and lipid head, and the water O-H M1 adopt the same orientation directions. The introduction of methanol into the lipid hydrophilic head group can strongly perturb the entire length of the alkyl chains, resulting that the signals of CD2 and CD3 groups from both leaflets can not cancel each other.
文摘Four-, six-, and eight-membered ring silica nanotubes at temperatures from 300 K to 1600 K are relaxed by classical molecular dynamics simulations with three potential models. The simulation results indicate that the stability of the end rings of the three silica nanotubes gradually decreases with increase in temperature. The validity of the vibrational features of silica nanotubes is shown by the vibrational density of states. Infrared spectra on the silica nanotubes under different temperatures are investigated. A detailed assignment of each spectral peak to the corresponding vibrational mode of the three nanotubes has been addressed. The results are in good agreement with the other theoretical and experimental
文摘Sum frequency generation vibrational spectroscopy (SFG-VS) is a robust technique for inter- facial investigation at molecular level. The performance of SFG-VS mostly depends on the spectral resolution of the SFG system. In this research, a simplified function was deduced to calculate the spectral resolution of picosecond SFG system and the lineshape of SFG spectra based on the Guassian shaped functions of IR beam and visible beam. The function indicates that the lineshpe of SFG spectra from nonresonant samples can be calculated by the Guassian widths of both IR beam and visible beam. And the Voigt lineshape of SFG spectra from vibrational resonant samples can be calculated by the Homogeneous broadening (Lorentzian width) and Inhomogeneous broadening (Guassian width) of vibrational modes, as well as the Guassian widths of both IR beam and visible beam. Such functions were also applied to verify the spectral resolution of the polarization-resolved and frequency-resolved picosecond SFG-VS system which was developed by our group recently. It is shown that the linewidths of IR beams that generated from current laser system are about 1.5 cm-1. The calculated spectral resolution of current picosecond IR scanning SFG-VS system is about 4.6 cm-1, which is consist with he spctral resolution shown in the spectra of cholesterol monolayer (3.5-5 cm-1).
基金A part of the results of the Project cosponsored by the Natural Scienee Fundation of China(49070127)the Chinese Academy of Geological Sciences(B8901)
文摘On the basis of the records of strong seismic events taking place in soft carbonate sediments, a new seismic sequence system of vibrational liquefaction is established, which consists of a series of units, such as escaped structure of micrite veins and liquefied deformation formed in the period of seismic liquefaction, land subsidence structure after liquefaction, tsunamic hummocky and turbidite produced by seismic events, This sequence is a generalization and summation of field observation in vast areas, which shows the whole process of a strong seismic event and provides an unified theoretical explanation. The pattern of the seismic sequence by vibrational liquefaction provides one of correlation standards for geologists in the field to discriminate events in carbonate sequences. Based on the pattern of seismic sequence, the authors first advance a new conception of the Palaeo-Tanlu (Tancheng-Lujiang) Zone and discuss primarily its geological significations.
文摘Resonant and nonresonant intermolecular vibrational energy transfers in Gdm- SCN/KSCN=1/1, GdmSCN/KS^13CN=1/1 and GdmSCN/KS^13C^15N=1/1 mixed crystals in melts and in aqueous solutions are studied with the two dimensional infrared spectroscopy. The energy transfers in the samples are slower with a larger energy donor/acceptor gap, independent of the Raman spectra. The energy gap dependences of the nonresonant energy transfers cannot be described by the phonon compensation mechanism. Instead, the experi- mental energy gap dependences can be quantitatively described by the dephasing mechanism. Temperature dependences of resonant and nonresonant energy transfer rates in the melts are also consistent with the prediction of the dephasing mechanism. The series of results suggest that the dephasing mechanism can be dominant not only in solutions, but also in melts (pure liquids without solvents), only if the molecular motions (translations and rotations) are much faster than the nonresonant energy transfer processes.