摘要:

A new semi-classical method for the calculation of perturbation-type integrals, recently presented by Child, is examined and applied to the calculation of rotationally and vibrationally inelastic distorted wave integrals in the He-H2systems. Using the uniform Airy approximation to the wavefunctions the system is mapped onto a model system and evaluation of the integral follows using stationary phase-type arguments. We have theoretically examined the stationary-point structure and the analysis was also used in the search for stationary points of the real system. Results of our investigation into the stationary-point structure of the system are presented along with the calculated integrals. Good agreement is found with exact calculations and comparison is also made with a recently developed analytical model.

ISSN:0026-8976    

DOI:10.1080/00268977800100441

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

We have measured the circular polarization of the iodine fluorescence induced by the 51450 Å argon ion laser line. The signs of the polarization of the rotationally resolved features have been used to assign the spectrum in the region of 5145 Å. We have identified and assigned nine separate fluorescence series excited by the 5145 Å line of the argon ion laser used in normal multi-mode operation. The main fluorescence doublets and the frequencies and polarizations of the rotational transfer features provide a stringent test of spectroscopic parameters and we have used our results to make a critical comparison of recently published constants.

ISSN:0026-8976    

DOI:10.1080/00268977800100451

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

We have studied quantitatively the circular polarization of rotationally resolved features in the laser-induced fluorescence from I2excited by the 5145 Å argon laser line, and its variation with various experimental parameters such as light intensity, iodine and foreign gas pressure. Optical pumping of the ν″ = 0,J″= 13 level of1Σg+has been unambiguously demonstrated and the variation ofCwith gas pressure has been analysed to yield cross sections for elastic and inelastic collisions which relax the oriented ground state. Experiments on the dipolar array of oriented3Π0u+molecules at very high pressures show that the circular polarization ratio does not change under conditions of many gas kinetic collisions per lifetime. This indicates that a selection rule ΔM= 0 operates on elastic collisions of I2* with other atoms and molecules, which appears to be rigorously adhered to.

ISSN:0026-8976    

DOI:10.1080/00268977800100461

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

A new method for molecular dynamics computer simulations, called the multiple time-step (MTS) method, is described, in which two or more time steps of different lengths are used to integrate the equations of motion in systems governed by continuous potential functions. With this method computing speeds have been increased by factors of three to eight over conventional molecular dynamics methods in simulations of monatomic and polyatomic fluids, with only marginal increases in computer storage.

ISSN:0026-8976    

DOI:10.1080/00268977800100471

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Semiclassical energy levels and frequencies are obtained for the ground electronic state of OCS using the potential of Foordet al.[10]. Certain rotational corrections were neglected, as explained in the text. The frequencies typically differ from the calculated quantal values by about 0·2 cm-1for the lower vibrational levels and about 2 cm-1for the higher ones. Fifty levels were obtained using 145 s of CDC 7600 computing time.

ISSN:0026-8976    

DOI:10.1080/00268977800100481

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Absolute intensities of the collision-induced Raman spectrum of argon are measured relative to certain rotational Raman lines of known intensity in hydrogen and nitrogen. Using the 4880 Å laser line for excitation and a detector sensitive to both polarizations, at a frequency shift of -12 wavenumbers, the cross section times unit volume and per unit wavenumber band, for scattering of light at right angles by binary pairs of argon atoms, is found to be 2·89 × 10-53cm6±7 per cent. Rigorous wave-mechanical computations on the basis of Placzek's polarizability theory predict a value of 2·83 × 10-53cm6±2 per cent and reproduce the experimental spectrum from about 6 to 60 wavenumbers, if the empirical MSV III potential is used together with the point-dipole model of the anisotropy of the polarizability tensor of two interacting atoms. For comparison, computations based on the rigorous classical trajectories of the collisions are presented. If the same potential function and model of the anisotropy are employed for frequency shifts larger than 10 wavenumbers, the classical treatment agrees with both experiment and wave-mechanical theory.

ISSN:0026-8976    

DOI:10.1080/00268977800100491

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Available models of the anisotropy of the polarizability of a pair of argon atoms are used to compute the collision-induced Raman spectrum. It is seen that the point-dipole model allows the best fit of the experimental frequency distribution and absolute intensity, which have been measured previously. Other models of the anisotropy appear by these criteria to be overcorrected or, if successful, not significantly different from the point-dipole expression.

ISSN:0026-8976    

DOI:10.1080/00268977800100501

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Depolarized Raman spectra of binary collisional pairs of atoms in krypton and xenon are obtained at gas densities of 1–10 amagat. Absolute intensities relative to a known rotational transition of nitrogen are determined. For light of 4880 Å wavelength incident in thex-direction, polarized in thez-direction and scattered in they-direction of a cartesian framex,y,z, at a frequency shift of -12 cm-1, the differential scattering cross section per unit wavenumber band times volume, is found to be 1·10 × 10-52cm6± 10 per cent for krypton, and 4·76 × 10-52cm6± 10 per cent for xenon, if the sum of both polarizations is considered. Wave-mechanical and classical computations reproduce both the shape and the intensity of the experimental spectra if the so-called point-dipole model of the anisotropy of the polarizability of collisional pairs of atoms is used. Other models of the anisotropy are seen to be overcorrected by these criteria.

ISSN:0026-8976    

DOI:10.1080/00268977800100511

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

A complete treatment of the spin hamiltonian for a pair of exchange coupled metal ions is given. The results obtained through the use of the Wigner-Eckart theorem are unrestricted with respect to the relative orientation of the single-ion tensors, and appropriate for both theS1=S2andS1≠S2cases. The necessary constants are derived so that matrix elements within a given spin multiplet can be treated by ordinary operator algebra with the coupled representation state vectors, |SM>, as a basis set. Explicit algebraic formulae for matrix elements between spin multiplets are presented for the first time. Symmetry restrictions are discussed in general and illustrated for the simple case of two ions related by an inversion centre, pair symmetryCi.

ISSN:0026-8976    

DOI:10.1080/00268977800100521

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Perturbation solutions are given to the spin-hamiltonian ℋ = βB. g. S+S. A. I+I. P. Ifor a system withS= 1/2 andI= 3/2, where all the tensors have the same principal axes. The resultant formulae are successfully applied to gold, iridium and osmium E.P.R. spectra where quadrupole interaction is large.

ISSN:0026-8976    

DOI:10.1080/00268977800100531

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor