摘要:

Partial and total valence- and inner-shell photoionization cross sections of HCl are calculated in the random phase approximation employing an extended basis set and the Stieltjes imaging procedure. Results of independent-channel as well as multi-channel calculations in the static-exchange approximation are reported for comparison. The generally good agreement with recent experimental measurements indicates that the random phase approximation provides an efficient description of photoionization channel coupling. The calculated vertical spectra in the ‘discrete’ region of valence- and inner-shell are also reported.

ISSN:0026-8976    

DOI:10.1080/00268978600102141

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Calculations of the transition probability for the two photon excitation from the ground to some of the first excited electronic states in both NH3and HF are presented. The transitions are taken to be vertical and a random molecular orientation is assumed. The transition moments needed to evaluate the transition amplitudes are computed by using the random phase approximation (RPA), that directly supplies the initial state-intermediate states one-electron transition density matrices and the excitation energies, while the intermediate states-final state one-electron transition density matrices are obtained from the RPA results through an equation of motion method (EMM) technique. The effect of mixing of the excitation channels is investigated. For each chosen final state enough data are supplied to give a thorough account of the dependence of the transition probability upon the polarization of the radiation and the experimental geometrical set-up. The calculations are performed using both the length and the velocity forms of the perturbing operator.

ISSN:0026-8976    

DOI:10.1080/00268978600102151

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The theory of magneto-spatial dispersional variations in refractive index and absorption index is extended to systems composed of diamagnetic molecules acted on by a d.c. electric field. The variations are discussed in their dependence on the electrical pure reorientation process and electric distortional-reorientational cross-process for molecules with the point group symmetries 3, 4, 6, ∞, 32, 422 and 622. In particular, an expression is derived for the magneto-chiral birefringence and dichroism in the presence of weak as well as very strong (saturation) electric molecular reorientation. At saturation reorientation the two effects are shown to be described by a lesser number of multipolar polarizability tensor components than in the case of weak molecular reorientation or in the absence of a d.c. electric field.

ISSN:0026-8976    

DOI:10.1080/00268978600102161

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Several results concerning the phase equilibria of two-centre Lennard-Jones (2CLJ) fluids are presented. Firstly, a comparison of chemical potential values for the elongationL= 0·63 obtained from perturbation theory shows qualitative agreement with the simulation results of Romano and Singer and excellent agreement with results of Guillot and Guissani except at the highest density. The complete saturation curve of the 2CLJ-0·63 fluid is then calculated by combining the Romano-Singer results, the Haar-Shenker-Kohler equation and perturbation theory. For the 2CLJ-fluids withL= 0·05, 0·10, and 0·20 the low-temperature saturation curves are calculated by perturbation theory as well as the pseudocritical points. At that point the packing fraction of the hard molecular cores has the constant value η = 0·165 in going fromL= 0 toL= 0·3292 and falls off slightly for higher elongations. The reduced hard sphere diameterd/σ, however, shows a distinct minimum at aboutL= 0·27.

ISSN:0026-8976    

DOI:10.1080/00268978600102171

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The rotational analysis of the origin bands of theÃ2Πu-[Xtilde]2Πgtransition of diacetylene and dideuterodiacetylene cations is considered. Although an analysis for diacetylene cation was made in 1956 by Callomon, some ambiguity remained concerning the absolute numbering and hence led to uncertainty in the derived constants. This situation has now been resolved by recording the emission spectra of this transition of the two isotopic cationic species rotationally cooled to ≈ 10 K in a supersonic free jet, as well as their rotationally resolved laser excitation spectra. By comparison of theQ-branch locations in the emission spectra, which only become discernible at such low temperatures, with those predicted using the two possible sets of constants, the rotational numbering is established. Consequently, the correct spectro-scopic constants of diacetylene and dideutero-diacetylene cations in their[Xtilde]2ΠgandÃ2Πuelectronic states are presented.

ISSN:0026-8976    

DOI:10.1080/00268978600102181

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Investigation of the magnetic field dependence of proton spin-lattice relaxation in solutions of bovine fibrinogen has been performed for Larmor frequencies between 50 Hz and 60 MHz, and complemented with measurements of spin-spin relaxation rates at 2 kHz and 25 MHz. A thorough analysis of experimental data, including the effects of protein concentration, temperature, pH and isotopic dilution, leads to an overall relaxation scheme consistent withT1andT2values at both low and high magnetic fields. The scheme involves water molecules slightly anisotropically bound on proteins as well as slow exchanging protein protons magnetically coupled to solute nuclei. A coherent picture, reminiscent of the traditional hydration layer, can be obtained for bound water. A major conclusion is that transfer of single protons may contribute substantially to the chemical exchange between free and bound water.

ISSN:0026-8976    

DOI:10.1080/00268978600102191

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Measurements of the proton spin-lattice relaxation rates for Larmor frequencies between 200 Hz and 60 MHz and of the spin-spin relaxation rates at 2 kHz and 25 MHz have been performed in three types of polymerized fibrin. The influence of aggregation-induced macromolecular dynamical hindrance on the relaxation behaviour is analysed and discussed. Special attention is given to the relaxation behaviour at low magnetic field, which results from a combined effect of macromolecular reorientation, hydration and chemical exchange between free and bound water. Further support is given to an overall relaxation scheme involving slow exchanging protein protons as well as slightly anisotropically bound water molecules. Bound water protons appear to relax mainly by intramolecular interaction and to exchange with free water protons through a thermally activated process with activation energy of ca 7·5 kJ mol-1.

ISSN:0026-8976    

DOI:10.1080/00268978600102201

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Combining neutron diffraction intermolecular scattering functions with RISM partial scattering function forX-XandX-Cl atom paris the Cl-Cl partial scattering functions are obtained. The systematic trends in Cl-Cl partial scattering functions and radial distribution functions in six different tetrachloride liquids have been investigated. The intermolecular nearest neighbour Cl-Cl distance of 0·377(14) nm corresponds well with the value of 0·34 nm adopted for the chlorine hard sphere diameter in the RISM calculations.

ISSN:0026-8976    

DOI:10.1080/00268978600102211

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The isotropic Raman spectrum of the molecule described by a three-level vibrational system has been simulated for a bath modeled as a two-state stochastic process. The influence of the energy relaxation as well as the dephasing on the spectrum is demonstrated for different modulation speeds of the bath. The cumulant expansion and the projection-operator formalism description of the isotropic spectrum have been studied. The results show that the projection-operator method provides an accurate description of these spectra for all modulation speeds whereas the cumulant expansion technique reproduces the spectra in the fast modulation limit only.

ISSN:0026-8976    

DOI:10.1080/00268978600102221

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A method is described which allows Coriolis coupling and rotor asymmetry effects to be included in coupled channel calculations on collisions involving near symmetric top molecules. The method is used to investigate energy transfer between thev6andv4vibrational levels of D2CO in collisions with the rare gas atoms He and Ar. Previously, this sytem has been investigated in double resonance experiments by Orr and coworkers. Our calculations indicate that vibrational relaxation in this system is greatly enhanced by Coriolis coupling, and approaches the rate of rotational relaxation.

ISSN:0026-8976    

DOI:10.1080/00268978600102231

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor