Photoelectron angular distributions of H ionization in low energy regime:Comparison between different potentials

We theoretically investigate the low energy part of the photoelectron spectra in the tunneling ionization regime by numerically solving the time-dependent Schrdinger equation for different atomic potentials at various wavelengths.We find that the shift of the first above-threshold ionization（ATI） peak is closely related to the interferences between electron wave packets,which are controlled by the laser field and largely independent of the potential.By gradually changing the short-range potential to the long-range Coulomb potential,we show that the long-range potential＇s effect is mainly to focus the electrons along the laser＇s polarization and to generate the spider structure by enhancing the rescattering process with the parent ion.In addition,we find that the intermediate transitions and the Rydberg states have important influences on the number and the shape of the lobes near the threshold.

Ionization energies and term energies of the ground states 1s^22s of lithium-like systems

We extend the Hamiltonian method of the full-core plus correlation （FCPC） by minimizing the expectation value to calculate the non-relativistic energies and the wave functions of ls22s states for the lithium-like systems from Z = 41 to 50. The mass-polarization and the relativistic corrections including the kinetic-energy correction, the Darwin term, the electron-electron contact term, and the orbit-orbit interaction are calculated perturbatively as first-order correction. The contribution from quantum electrodynamic （QED） is also explored by using the effective nuclear charge formula. The ionization potential and term energies of the ground states 1 s22s are derived and compared with other theoretical calculation results. It is shown that the FCPC methods are also effective for theoretical calculation of the ionic structure for high nuclear ion of lithium-like systems.

Theoretical study of γ-aminobutyric acid conformers:Intramolecular interactions and ionization energies

Allowing for all combinations of internal single-bond rotamers, 1,296 unique trial structures of γ-Aminobutyric acid （GABA） are obtained. All of these structures are optimized at the M06-2X level of theory and a total of 68 local minimal conformers are found. The nine low-lying conformers are used for further studies. According to the calculated relative Gibbs free energies at M06-2X level of theory, we find that the dispersion is important for the relative energy of GABA. The intramolecular hydrogen bonds and byperconjugative interaction and their effects on the conformational stability are studied. The results show that both of them have great influence on the conformers. The vertical ionization energies （VIE） are calculated and match the experimental data well. The results show that the neutral GABA in the gas phase is a multi-conformer system and at least four conformations exist.

Synchrotron radiation VUV double photoionization of some small molecules

The VUV double photoionizations of small molecules （NO, CO, CO2, CS2, OSC and NH3） were investigated with photoionization mass spectroscopy using synchrotron radiation. The double ionization energies of molecules were determined with photoionization efficiency spectroscopy. The total energies of these molecules and their parent dications （NO^2＋,CO^2＋,CO2^2＋, CS2^2＋, OSC^2＋and NH^2＋） were calculated using the Gaussian O3 program and Gaussian 2 （NO^2＋, CO^2＋, CO2^2＋,CS2^2＋,OSC^2＋ and NH3^2＋） were calculated using the Gaussian 03 program and Gaussian 2 calculations. Then, the adiabatic double ionization energies of the molecules were predicated by using high accuracy energy mode. The experimental double ionization energies of these small molecules were all in reasonable agreement with their respective calculated adiabatic double ionization energies. The mechanisms of double photoionization of these molecules were discussed based on a comparison of our experimental results with those predicted theoretically. The equilibrium geometries and harmonic vibrational frequencies of molecules and their parent dications were calculated by using the MP2 （full） method. The differences in configurations between these molecules and their parent dications were also discussed on the basis of theoretical calculations.

UV Photoionization Study of the Ethyl Radical

The ethyl radical was observed in a low-pressure premixed gasdine/oxygen/argon flame by using tunable vacuum ultraviolet photoionization mass spectrometry. The ionization energy（IE） of the ethyl radical was derived to be（8. 24 ± 0. 02） eV from the photoionization efficiency curve. In addition, a high-level ab initio Gaussian-3 （G3） method was used to calculate the energies of the radical and its cation. The calculated adiabatic ionization potential is 8. 17 eV, which is in good agreement with the experimental value.

Dependence of Decamethylcyclopentasiloxane (DMCPS) Dissociation on Ionized Energy by Using Quadrupole Mass Spectrum

Dependence of decamethylcyclopentasiloxane （DMCPS） organosilicon dissociation on ionized energy in the energy range of 25 eV to 70 eV is investigated by using a quadrupole mass spectrometry. At the ionized energy below 55 eV, the dissociation of DMCPS is dominant. As the ionized energy is above 55 eV, the DMCPS dissociation achieves the maximum cross section, while the fragments from the DMCPS dissociation can further dissociate, which leads to a different ingredient of fragments. At the lower ionized energy of 25 eV, the main fragments are SiOC2H＋, SiCH＋, Si＋, O＋ and CH＋ ions, which shows an important effect on the SiCOH low-k film deposition.

Suppression and compensation effect of oxygen on the behavior of heavily boron-doped diamond films

This work investigates the suppression and compensation effect of oxygen on the behaviors and characteristics of heavily boron-doped microwave plasma chemical vapor deposition(MPCVD)diamond films.The suppression effect of oxygen on boron incorporation is observed by an improvement in crystal quality when oxygen is added during the diamond doping process.A relatively low hole concentration is expected and verified by Hall effect measurements due to the compensation effect of oxygen as a deep donor in diamond.A low acceptor concentration,high compensation donor concentration and relatively larger acceptor ionization energy are then induced by the incorporation of oxygen;however,a heavily boron-doped diamond film with high crystal quality can also be expected.The formation of an oxygen–boron complex structure instead of oxygen substitution,as indicated by the results of x-ray photoelectron spectroscopy,is suggested to be more responsible for the observed enhanced compensation effect due to its predicted low formation energy.Meanwhile,density functional theory calculations show that the boron–oxygen complex structure is easily formed in diamond with a formation energy of-0.83 eV.This work provides a comprehensive understanding of oxygen compensation in heavily boron-doped diamond.

Possible Evolutionary Models in the Initially Hydride Earth Theory

A modern view of the properties of chemical elements has confirmed the theory of the hot origin of the Earth. The next step in developing this theory was the hypothesis of the initial hydride Earth. In this work, we attempted to find additional evidence for this hypothesis and show additional effects that flow from it. The effect of the physical properties of atoms and ions on their behavior during the formation of the Earth was studied. The maximum contribution to the distribution of elements was made by those elements whose content in the original protoplanets of the disk was the maximum. Correlation dependence is obtained, which allows one to calculate the distribution of elements in the protoplanetary disk. It was shown that hydrogen was the main element in the proto substance located in the zone of the Earth’s formation. In this case, various chemical compounds formed, most represented by hydrogen compounds—hydrides. Since the pressure inside the Earth is 375 GPa, this factor forces the chemical compounds to adopt stoichiometry and structure that would not be available in atmospheric conditions. It is shown that many chemical elements at high pressure in a hydrogen medium form simple hydrides and super hydrides—polyhydrides with high hydrogen content. Pressure leads to a higher density of matter inside the planet. Given the possibility of forming polyhydrides, there is the possibility of binding the initially available hydrogen in an amount that can reach 49.3 mole%. Young Earth could contain about 10.7 mass% of hydrogen in hydrides, polyhydrides, and adsorbed form is almost twice higher than previous estimates. This fact additionally confirms the theory of the original hydride Earth. In hydrides, the occurrence of the phenomenon of superconductivity was discovered. Polyhydrides were shown as potential superconductors with a high critical temperature above 200 K. We, based on these data, hypothesized the presence of superconducting properties in the Earth’s core, which explains the presence of a magnetic field in the Earth, as well as the unevenness and instability of this field and the possibility of migration of the Earth’s poles. The fact that the Earth has a hydroid core causes its change in time due to the instability of hydrides. Arranged several possible models of the destruction of the Earth’s core. The calculations showed that both models give close results. These results give predictions that can be measured. The proposed models also made it possible to estimate the initial size of the Earth. Possible ways of further testing the hypothesis of the initial hydride Earth is shown.

Molecular Structure, Vibrational Spectrum and Ionization Energy of m-Dimethoxybenzene

The optimized molecular geometries of the three rotamers of m-dimethoxybenzene in the ground So and electronically excited Sl states were predicted by ab initio and density functional theory （DFF） calculations. Their vibrational spectra in the St state were studied by one color resonant two photon ionization （1C-R2PI） method, and their ionization energies were measured by two color resonant two photon ionization （2C-R2PI） experiment. The optimized molecular geometries showed that the total energy of conformer a was the lowest in the So state. Most of the active vibrations assigned from the 1C-R2PI spectrum were found to be of the in-plane ring modes. The ionization energies （IE） of conformers a, b and c were determined to be 63521, 64487 and 63755 cm^-1, respectively.

Experimental and calculated momentum densities for the complete valence orbitals of the antimicrobial agent diacetyl

The first electronic structural study of the complete valence shell binding energy spectra of the antimicrobial agent diacetyl, encompassing both the outer and inner valence regions, is reported. The binding energy spectra as well as the individual orbital momentum profiles have been measured by using a high resolution （e, 2e） electron momentum spectrometer （EMS） at an impact energy of 1200eV plus the binding energy, and using symmetric noncoplanar kinematics. The experimental orbital electron momentum profiles are compared with self-consistent field （SCF） theoretical profiles calculated using the Hartree-Fock approximation and Density Functional theory predictions in the target Kohn-Sham approximation which includes some treatment of correlation via the exchange and correlation potentials with a range of basis sets. The pole strengths of the main ionization peaks from the inner valence orbitals are estimated.

How to characterize capacitance of organic optoelectronic devices accurately

The selection of circuit model（i.e., parallel or series model） is critical when using a capacitance–frequency and capacitance–voltage technique to probe properties of organic materials and physical processes of organic optoelectronic devices. In the present work, capacitances of ITO/Alq3/Al and ITO/CuPc/Al are characterized by series and parallel model,respectively. It is found that the large series resistance comes from the ITO electrode and results in the inapplicability of the parallel model to measuring the capacitances of organic devices at high frequencies. An equivalent circuit model with consideration of the parasitical inductance of cables is constructed to derive the capacitance, and actual capacitance–frequency spectra of Alq3 and CuPc devices are obtained. Further investigation of temperature-dependent capacitance–frequency and capacitance–voltage characteristics indicates that CuPc and Al form the Schottky contact, the density and ionization energy of impurities in CuPc are obtained. Moreover, more practical guidelines for accurate capacitance measurement are introduced instead of the impedance magnitude, which will be very helpful for the organic community to investigate capacitance-related characteristics when dealing with various organic optoelectronic devices.

Spin-orbit ab initio curves of ^(80)Se_2^+ ion and the assignment of photoelectron spectra of ^(80)Se_2 molecule

This paper carries out ab initio calculations to study the ^80Se2（X^3Σg^-） state and ^80Se2^＋（X^2Πg）, ^80Se2^＋（a^4Πg） states by using completed active space self-consistent field and multi-reference second order perturbation theory. The electronic curves of these states including spin-orbit coupling are calculated, and then the spectroscopic parameters are obtained. The photoelectron spectra of ^80Se2 molecule in gas phase are assigned according to Franck-Condon analysis based on calculated potential energy curves. The ionization energies of ^80Se2 molecule are determined by the present calculation.

Structural and Spectroscopic Properties of Linear Carbon Chains NC_(2n)N and HC_(2n+_1)N(n=1～10)

Using density functional theory, geometries and vibrational frequencies of linear chains NC2nN and HC2n＋1N （n = 1 - 10） have been investigated. Time-dependent density functional theory （TD-DFF） has been used to calculate the vertical transition energies and oscillator strengths for the x^1∑g^＋→I^1∑u^＋ transition in NC2,N （n = 1 -10） and X^1∑ → I^1∑^＋ transition in HC2n＋1N （n =1 -7）. On the basis of present calculations, the explicit expressions for the size dependence of the excitation energy and the first adiabatic ionization energy in both carbon chains have been suggested.

Orbital responses to methyl sites in C_nH_(2n+2) (n=1-6)

Orbital responses to methyl sites in CnH2n＋2 （n = 1-6） are studied by B3LYP/TZVP based on the most stable geometries using the B3LYP/aug-cc-pVTZ method. Vertical ionization energies are produced using the SAOP/et-pVQZ model for the complete valence space. The highest occupied molecular orbital （HOMO） investigations indicate the p- electron profiles in methane, ethane, propane, and n-butane. By increasing the number of carbon-carbon bonds in lower momentum regions, the s, p-hybridized orbitals are built and display strong exchange and correlation interactions in lower momentum space （P 〈 0.50 a.u.）. Meanwhile, the relative intensities of the isomers in lower momentum space show the strong bonding number dependence of the carbon-carbon bonds, meaning that more electrons have contributed to orbital construction. The study of representative valence orbital momentum distribution further confirms that the structural changes lead to evident electronic rearrangement over the whole valence space. An analysis based on the isomers reveals that the valence orbitals are isomer-dependent and the valence ionization energy experiences an apparent shift in the inner valence space. However, such shifts are greatly reduced in the outer valence space. Meanwhile, the opposite energy shift trend is found in the intermediate valence space.

Exchange-Correlation Functional Comparison of Electronic Energies in Atoms Using a Grid Basis

Calculation of total energies of the electronic ground states of atoms forms the basis for the frozen-core pseudopotentials used in atomistic calculations of much larger scale. Reference values for these energies provide a benchmark for the validation of new software to calculate such potentials. In addition, basic atomic-scale electronic properties such as the (first) ionization energy provide a simple check on the approximation used in the calculation method. We present a comparison of the total energies and ionization energies of atoms Z = 1 - 92 calculated in density functional theory with several levels of exchange-correlation functional and the Hartree-Fock method, comparing ionization energies to experiment. We also investigate the role of relativistic treatment on these energies.

Conformation effects on the molecular orbitals of serine

This paper calculates the five most stable conformers of serine with Hartree-Fock theory, density functional theory （B3LYP）, Moller-Plesset perturbation theory （MP4（SDQ）） and electron propagation theory with the 6-311＋＋G（2d,2p） basis set. The calculated vertical ionization energies for the valence molecular orbitals of each conformer are in agreement with the experimental data, indicating that a range of molecular conformations would coexist in an equilibrium sample. Information of the five outer valence molecular orbitals for each conformer is explored in coordinate and momentum spaces using dual space analysis to investigate the conformational processes, which are generated from the global minimum conformer Serl by rotation of C2-C3 （Ser4）, C1 C2 （Ser5） and C1-O2 （Set2 and Ser3）. Orbitals 28a, 27a and 26a are identified as the fingerprint orbitals for all the conformational processes.

Identification of deuterons at BESIII

The identification of deuterons with momenta in the range of 0.52−0.72 GeV/c is studied with specific ionization energy loss information using a data sample collected by the BESIII detector at center-of-mass energies between 4.009 and 4.946 GeV.Clean deuteron samples are selected using time of flight information.For all data samples,the deuteron identification efficiencies are higher than 95%,with a maximum difference of%between data and Monte Carlo simulation.This verifies the effectiveness of the deuteron identification method based on specific ionization energy loss and provides valuable information for future studies on processes involving deuterons in the final state at BESIII.

Calculations of ionization energies and electron affinities for atoms and molecules: A comparative study with different methods

In the present work,we examined the performance of 36 density functionals,including the newly developed doubly hybrid density functional XYG3(Y.Zhang,X.Xu,and W.A.Goddard Ⅲ,Proc.Natl.Acad.Sci,USA,2009,106,4963),to calculate ionization energies(IEs)and electron affinities(EAs).We used the well-established G2-1 set as reference,which contains 14 atoms and 24 molecules for IE,along with 7 atoms and 18 molecules for EA.XYG3 leads to mean absolute deviations(MADs)of 0.057 and 0.080 eV for IEs and EAs,respectively,using the basis set of 6-311+G(3df,2p).In comparison with some other functionals,MADs for IEs are 0.109(B2PLYP),0.119(M06-2X),0.159(X3LYP),0.161(PBE),0.162(B3LYP),0.165(PBE0),0.173(TPSS),0.200(BLYP),and 0.215 eV(LC-BLYP).MADs for EAs are 0.090(X3LYP),0.090(B2PLYP),0.102(PBE),0.103(M06-2X),0.104(TPSS),0.105(BLYP),0.106(B3LYP),0.126(LC-BLYP),and 0.128 eV(PBE0).

Charged particles:Unique tools to study irradiation resistance of concentrated solid solution alloys

Many multicomponent concentrated solid solution alloys(CSAs),including high-entropy alloys(HEAs),exhibit improved radiation resistance and enhanced structural stability in harsh environments.To study and assess irradiation resistance of nuclear materials,energetic ion and electron beams are commonly used to create displacement damage.Moreover,charged particles of ions,electrons,and positrons are unique tools to create and characterize radiation effects.Ion beam analysis(e.g.,Rutherford backscattering spectrometry,nuclear reaction analysis,and time-of-flight elastic recoil detection analysis),electron microscopy techniques(e.g.,transmission or scanning electron microscopy,and electron diffraction),and positron annihilation spectroscopy have been applied to characterize irradiated CSAs or HEAs to understand defect formation and evolution together with chemical and microstructural information.Their distinctive analyzing power and some perspectives in these techniques are reviewed.In developing structural alloys desirable for applications in advanced reactors,neutron exposure is a critical test but the limitation in achievable high damage levels is,however,a bottleneck.Ion irradiation is often used as a surrogate for neutron irradiation,and the associated reduced transmutations and higher displacements per atom(dpa)rates are desirable for materials research.Nevertheless,cautions need to be taken when relying on ion irradiation results for reactor evaluations.Literature on differences between ions and neutrons is briefly reviewed.In addition,the links to bridge the current advances on fundamental understandings to reactor applications are discussed to lay the groundwork between neutrons and ions for radiation effects studies.

Dopant atoms as quantum components in silicon nanoscale devices

Recent progress in nanoscale fabrication allows many fundamental studies of the few dopant atoms in various semiconductor nanostructures. Since the size of nanoscale devices has touched the limit of the nature, a single dopant atom may dominate the performance of the device. Besides, the quantum computing considered as a future choice beyond Moore＇s law also utilizes dopant atoms as functional units. Therefore, the dopant atoms will play a significant role in the future novel nanoscale devices. This review focuses on the study of few dopant atoms as quantum components in silicon nanoscale device. The control of the number of dopant atoms and unique quantum transport characteristics induced by dopant atoms are presented. It can be predicted that the development of nanoelectronics based on dopant atoms will pave the way for new possibilities in quantum electronics.