• Abstract

4-hydroxy-l-proline is formed by hydroxylation of proline, an amino acid found in protein, whose inhibition results in hair problems in human, causing scurvy disease. We report a theoretical study on cis and trans conformers of 4-hydroxy-lproline using first principle density functional approach at B3LYP/6-31+G(d,p) level. The equilibrium structures of both conformers are obtained to analyze their vibrational properties. The calculated vibrational modes are assigned and interpreted on the basis of potential energy distribution analysis. A good correlation has been obtained between calculated frequencies and corresponding experimental values from FTIR spectra. The electronic properties of both conformers are also calculated and discussed.

• Abstract

In this article, we do a research on the chiral shift process of the isolated alpha alanine molecule using the basis set of 6-31+g(d,p), which is based on density functional theory B3LYP. Furthermore, the chiral transition path reaction potential energy surface of ibuprofen molecule is drawn by looking for the extreme value point structure including the transition state and intermediate. Finally, the geometry and electronic structure properties of extreme value point are also analyzed. The results show that there are two achieve reaction paths of ibuprofen from S-type to R-type. Path 1 consists of three transition states and two intermediate states. Path 2 includes four transition states and three intermediate states. On the reaction path, the greatest barrier which is from the transfer of hydrogen in chiral carbon to oxygen in carboxyl, is 73.54 Kcal/mol. The research provides a theoretical reference to further realize some important application value over the chiral transition reaction control of point chiral molecule.

• Abstract

The potential energy curves (PECs) of X¹Σ^+, a,³Σ^+, a³∏, A¹∏ states for GeO molecule are calculated by themultireference configuration interactionmethod (MRCI) and MRCI with the Davidson's corrections (MRCI+Q) with aug-cc-pVTZ basis set. All these states involved dissociate into the same dissociation channel Ge(³P)+O(³P). For the four states, the spectroscopic parameters (R_e, D_e, ω_e, B_e, ω_eχ_e and T_e) have been obtained, which shows that our results are in very good agreement with the experimental value and other theoretical data at MRCI+Q level. The dipole moments of these states are also obtained. In addition, based on the accurate results of spectroscopic constants atMRCI+Q level, the first 30 vibrational states are determined for the four low-lying electronic states when J=0. The vibrational levels G(v) and inertial rotation constants Bv at MRCI+Q level are calculated when J=0, the results of X¹Σ^+ and A¹∏ states are in concordance with the available other theoretical values and experimental work. The dissociation limits, dissociation energies, electronic configurations at equilibriuminternuclear distance for a,³Σ^+, a³∏ states also are predicted for the first time.

• Abstract

We present the distorted wave Born approximation (DWBA) for electron impact excitation and amethod to calibrate the DWBA.With the calibrated DWBA, the differential cross sections (DCS) for excitation of H and He^+ from 1s to 2s and 2p are calculated and the results are comparedwith the absolute experimentalmeasurements for H at incident energies of 50 eV and 100 eV. It has been found that the theoretical results are in very good agreement with the experiment, which confirms the validity of the calibration procedure. This work prepares an efficient theoretical method for numerical simulations of non-sequential double ionization of He in strong laser pulse in which laser-induced electron impact excitation of He^+ is involved.

• Abstract

Using the density functional B3P86/cc-PV5Z method, the geometric structure of AlH molecule under different external electric fields are optimized, and the bond lengths, dipole moments, vibration frequencies and other physical properties parameters are obtained. The potential energy curves under different external fields are also obtained by CCSD(T) method with the same basis set. These results show that the properties parameters and potential energy curves may change with different external electric field, especially in the reverse electric fields. The potential energy function without external electric field is fitted by Morse potential, and the potential energy curves under different external fields are fitted using constructed potential model, which adopted the dipole approximation theory. It is found that the fitting parameters are good agreement with experimental values and the critical dissociation electric parameter is consistent with numerical calculation. These results will provide important theoretical and experimental reference for further studying the molecular spectrum, dynamics and molecular cooling with Stark effect.

• Abstract

The Loschmidt echo of single qubit coupling to the environment for dimerized anisotropic XY spin chain in transverse field have been analyzed. We have obtained analytical expression for the Loschmidt echo. By numerically computing the Loschmidt echo, we find that the decay of coherence will be enhanced with the increasing of the staggered parameter.

• Abstract

Both non-homogenization treatment Zr, Ga addition and ternary Strip Casting alloy flakes can be used to prepare anisotropy HDDR NdFeB magnetic powders. This illustrates that anisotropy formation of magnetic powders neither depends on element addition nor depends on homogenization heat treatment of SC flakes. But the HDDR process procedure also plays an important role in anisotropy inducement. Highly anisotropic magnetic powders are attributed to rapid disproportionation reaction course, slow desorption-recombination reaction course, and optimum recombination hydrogen pressure during HDDR procedure process. This paper will provide an important guidance for preparing highly anisotropy magnetic powders with low cost.

• Abstract

In low birefringence fiber, by solving the coupled nonlinear Schrodinger equations contained the Raman effect for satisfy right- and left-handed circularly polarized light in the quasi-CW case, the relationship between the effective polarization beat length and changes of input power have been studied emphatically in low- and high input power situation considering the Raman effect or not. The results showed that the polarization state evolution cycles of the incident light can be changed and meanwhile the transmission distance of the incident light also can be changed due to Raman effect, regardless of the polarization of the incident light was along the slow axis or along the fast axis.

• Abstract

The theoretical modified Khare (BEB) model has been used to calculate the total cross sections for L_1, L_2 and L_3-subshells ionization of gold atom due to electron and positron impact for projectile energy varying fromthe threshold of ionization to 60 times the threshold energy For L subshells the present cross section due to electron and positron impact cross sections are in remarkable agreement with available experimental data and other theoretical cross sections. Total L shell ionization cross sections have been also calculated in the energy varying from the threshold of ionization to several MeV by electron impact. It is found good agreement with available experimental data. The investigation for other atoms is in progress.