Simultaneous measurements of global vibrational spectra and dephasing times of molecular vibrational modes by broadband time-resolved coherent anti-Stokes Raman scattering spectrography

In broadband coherent anti-Stokes Raman scattering （CARS） spectroscopy with supercontinuum （SC）, the simultaneously detectable spectral coverage is limited by the spectral continuity and the simultaneity of various spectral components of SC in an enough bandwidth. By numerical simulations, the optimal experimental conditions for improving the SC are obtained. The broadband time-resolved CARS spectrography based on the SC with required temporal and spectral distributions is realised. The global molecular vibrational spectrum with well suppressed nonresonant background noise can be obtained in a single measurement. At the same time, the measurements of dephasing times of various molecular vibrational modes can be conveniently achieved from intensities of a sequence of time-resolved CARS signals. It will be more helpful to provide a complete picture of molecular vibrations, and to exhibit a potential to understand not only both the solvent dynamics and the solute-solvent interactions, but also the mechanisms of chemical reactions in the fields of biology, chemistry and material science.

Dynamical correlation between quantum entanglement and intramolecular energy in molecular vibrations:An algebraic approach

The dynamical correlation between quantum entanglement and intramolecular energy in realistic molecular vibrations is explored using the Lie algebraic approach. The explicit expression of entanglement measurement can be achieved using algebraic operations. The common and different characteristics of dynamical entanglement in different molecular vibrations are also provided. The dynamical study of quantum entanglement and intramolecular energy in small molecular vibrations can be helpful for controlling the entanglement and further understanding the intramolecular dynamics.

MOLECULAR DYNAMICS SIMULATION OF POLISHING PROCESS BASED ON COUPLING VIBRATIONS OF LIQUID

Molecular dynamics method is applied to study the machining mechanisms of polishing based on coupling vibrations of liquid. The physical phenomena of abrasive particles bombarding on silicon monocrystal surface are simulated using Tersoff potentials. The effects of vibration parameters, particle size, incident angle and particle material are analyzed and discussed. Material removal mechanisms are studied. Deformation and embedment phenomena are found in the simulations, Bombardment will destroy the crystal structures near the impact point, and adhesion effect is responsible for final removal of material.

Vibrational Spectra and Density Functional Theory Calculations of Metallotriphenylcorroles

The infrared absorption and Raman scattering spectra were measured for the metallotriph- enylcorroles （MTPCs, M=Cu, Co, Ni, Mn）. The ground-state structures and vibrational spectra of MTPCs have been calculated with the density functional theory. The observed Raman and IR bands have been assigned based on the calculation results. Due to the symmetry lowering, the vibrational spectra of MTPCs are much more complex than metal- loporphyrins, and several skeletal modes are found strongly coupled to the phenyl vibrations. The relationship between the Raman/IR frequencies and the structures of TPC ring is in-vestigated. It is found that the vibrations involving the Cα^I Cα^I stretch and CαCm stretchare sensitive to the size of corrole core. In particular, the frequency of v5, which is assigned to Cα^I Cα^I stretch in coupling with the CαCm symmetric stretch, increases linearly with the decrease of the corrole core-sizes and may be used as a mark band to evaluate the structural change of the metallocorroles.

Vibrational Spectra and Density Functional Theory Calculations of Metallo-tetra- （tert-butyl）-tetra-azaporphyrines

The infrared absorption and 514.5 nm excited Raman spectra were measured for the metallo- tetra-（tert-butyl）-tetraazaporphyrin （MT（tBu）TAP, M--Cu, Co, Ni, Zn）. The ground-state structures and vibrational spectra of MT（tBu）TAPs have been calculated at the B3LYP level of theory. The observed Raman and IR bands have been assigned based on the calculation results and by comparing with the normal metalloporphyrins. The relationship between the Raman/IR frequencies and the structures of TAP ring was investigated. The results show that the frequencies of CβCβ′ stretch （Ag）, asymmetric CaNto stretch （Ag）, and symmetric CaNto stretch （Bg） modes increase linearly with the decrease of the core-sizes of TAP ring. Among the three modes, the later two are more sensitive to the core-size change.

Resonance Raman Study of Aggregated Meso-tetra（4-pyridinium）porphyrin Diacid

Resonance Raman spectra of aggregated meso-tetra（4-pyridinium）porphyrin diacid （H8TPyP^6＋） were studied with excitation near the exciton absorption bands of 470 nm. The UV-Vis absorption and resonance light scattering spectra of HsTPyP^6＋ monomers and aggregates were also measured. The observed Raman bands of monomeric and aggregated HsTPyP^6＋ were assigned on the basis of the observed deuteration shifts and by comparing with the Raman spectra of analogous porphyrin diacids. Aggregation causes moderate downshifts （2-6 cm^-1） for high-frequency modes involving the in-plane CC/CN stretches of the porphyrin core and a dramatic upshift （12 cm^-1） for the out-of-plane saddling mode of the porphyrin ring. The structural changes induced by aggregation and the possible hydrogen bonding interaction between the HsTPyP^6＋ molecules in the aggregate are discussed based on the spectral observations.

Construction of an operando dual-beam fourier transform infrared spectrometer and its application in the observation of isobutene reactions over nano-sized HZSM-5 zeolite

An operando dual‐beam Fourier transform infrared (DB‐FTIR) spectrometer was successfully developed using a facile method. The DB‐FTIR spectrometer is suitable for the real‐time study of the dynamic surface processes involved in gas/solid heterogeneous catalysis under real reaction conditionsbecause it can simultaneously collect reference and sample spectra. The influence of gas‐phasemolecular vibration and heat irradiation at real reaction temperatures can therefore be eliminated.The DB‐FTIR spectrometer was successfully used to follow the transformation of isobutene over nano‐sized HZSM‐5 zeolite under real reaction conditions.

Experimental and Density Functional Theory Calculation Studies on Raman and Infrared Spectra of 1,1＇-Binaphthyl-2,2＇-diamine

The IR absorption, visible excited normal Raman, and UV-excited near-resonant Raman （UVRR） spectra of 1,1＇-binaphthyl-2,2＇-diamine （BINAM） were measured and analyzed. Density functional theory calculations were carried out to investigate its vibrational frequencies, infrared absorption, normal Raman, and near-resonance Raman intensities. The observed Raman and IR bands of BINAM were assigned with respect to the local vibrations of substituted 2-naphthylamine. Several Raman bands of BINAM were found selectively enhanced in the UVRR in comparison with the normal Raman spectrum. Possible excited state geometry distortion was discussed based on the resonance Raman intensity analysis.

Research on the characteristics of atmospheric air dielectric barrier discharge under different square wave pulse polarities

Energy efficiency limits the application of atmospheric pressure dielectric barrier discharge(DBD),such as air purification,water treatment and material surface modification.This article focuses on the electrical and optical effects of the DBD under three square wave pulses polarities-positive,negative and bipolar.The result shows that under the same voltage with the quartz glass medium,the discharge efficiency of bipolar polarity pulse is the highest due to the influence of deposited charge.With the increase of air gap distance from 0.5 to 1.5 mm,average power consumed by the discharge air gap and discharge efficiency decrease obviously under alumina,and increase,and then decrease under quartz glass and polymethyl methacrylate(PMMA).Through spectrum diagnosis,in the quartz glass medium,the vibration temperature is the highest under negative polarity pulse excitation.Under bipolar pulse,the vibration temperature does not change significantly with the change of air gap distance.For the three dielectric materials of quartz glass,alumina and PMMA,the molecular vibration temperature is the highest under the quartz glass medium with the same voltage.When the gap spacing,pulse polarity or dielectric material are changed,the rotational temperature does not change significantly.

Raman and Infrared Spectra for All-trans-astaxanthin in Dimethyl Sulfoxide Solvent

The Raman and infrared spectra of all-trans-astaxanthin （AXT） in dimethyl sulfoxide （DMSO） solvent were investigated experimentally and theoretically. Density functional cal-culations of the Raman spectra predict the splitting of the υ1 band into υ1-1 and υ1-2 compo-nents. The absence of splitting in Raman experimental spectra is ascribed to the competition between the two symmetric C=C stretching vibrations of the backbone chain. The υ1 band is very sensitive to the excitation wavelength： resonance excitation stimulates the higher-frequency υ1-2 mode, and off-resonance excitation corresponds to the lower-frequency υ1-1 mode. Analyses of the intramolecular hydrogen bonding between C=O and O-H in the AXT/DMSO system reveal that the C4=O1...H1-O3 and C4＇=O2...H2-O4 bonds are strengthened and weakened, respectively, in the electronically excited state compared with those in the ground state. This result reveals significant variations of the AXT molecular structure in different electronic states.

Single-molecule surface-enhanced Raman scattering： Current status and future perspective

The single-molecule surface-enhanced Raman scattering （smSERS） has been extensively studied after the initial observation in 1997, yet there still exist unsettled issues in the fundamental mechanism of smSERS. In this review, we survey some of the recent breakthroughs in the mechanism of smSERS and its application.

Effect of the ratio of transition dipole moments on few-cycle pulse propagation

Propagation of a few-cycle laser pulses in a dense V-type three-level atomic medium is investigated based on full-wave Maxwell-Bloch equations by taking the near dipole-dipole （NDD） interaction into account. We find that the ratio, γ of the transition dipole moments has strong influence on the time evolution and split of the pulse： when γ≤ 1, the NDD interaction delays propagation and split of the pulse, and this phenomenon is more obvious when the value of γ is smaller; when γ =√2, the NDD interaction accelerates propagation and split of the pulse.

Photo-acoustic spectrum and detection of nitrogen dioxide

The photo-acoustic （PA） spectrum of nitrogen dioxide （NO2） in the range of 420 - 520 nm with a Nd：YAG pumped optical parametric generator and amplifier as radiation source is presented. The spectrum has a characteristic of banded structure superimposed on continuum. The banded structure of the spectrum can be assigned to NO2 B2B1← X^2A1 transition. While the continual one comes from the chaos states of the first excited state A^2B2 and the high vibration levels of the ground state X^2A1. The relationship of PA signal with buffer gas pressure and NO2 concentration is measured. The PA signal intensity increases with buffer gas pressure and almost is invariable when the buffer gas pressure is more than 3.00 × 10^4 Pa. The PA signal intensity has linearity with NO2 concentration. The detection limit is about 2×10^-5 on the basis of SNR = 1, however lower value of the detection limit can be expected by improving the apparatus properties.

A procedure of determining potential energy surfaces of triatomic molecules from inversion of spectroscopic data

In this paper, we have suggested an iterative procedure of optimization of the linear parameters in an analytic potential energy function for a triatomic molecule, by combining both variational and second order perturbation methods. The most important feature of this procedure is that the objective function is an analytical expression which can be optimized easily. The application to the water molecule is presented.