摘要:

Transitions in the fundamental and first hot bands of the GeH radical have been detected previously by CO laser magnetic resonance. The transitions occur within both2Π3/2and2Π1/2manifolds. Additional resonances associated with the R(1/2) transition in the2Π1/2component are reported in this paper. These data have been fitted with previously published data for GeH and GeD to determine the parameters of a single model effective Hamiltonian which describes all naturally occurring isotopomers.

ISSN:0026-8976    

DOI:10.1080/00268979300100211

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The proton affinity of N2O has been calculated with the combination of theoretical methods called Gaussian-1 theory (567·7 kJ mol-1) and Gaussian-2 theory (570·4 kJ mol-1). The site of protonation at the highest levels of theory (G1 and G2 theory) is predicted to be oxygen; however, this prediction is very sensitive to the level of electron correlation. At MP3, MP4SDQ, and QCISD(T) levels of electron correlation, O protonation is preferred, whereas at MP2 and MP4SDTQ levels, N protonation is preferred. At the MP4 level, the effect of triple excitations on relative energies is overestimated and strongly favors the HNNO+isomer over the HONN+isomer. At the QCISD level, the effect of triple excitations also favors the HNNO+isomer, but it is not sufficiently large to cause the N protonated isomer to become more stable. Evidence is presented indicating that biradical character in HNNO+leads to a nonlinear NNO bond angle.

ISSN:0026-8976    

DOI:10.1080/00268979300100221

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Gibbs ensemble simulation data for Stockmayer fluids with μ*2= 3·0 and μ*2= 4·0 in the reduced temperature range of 0·77 (resp. 0·80)-0·98 and presented and compared with predictions based on the perturbation theories of Stell, G., Rasaiah, J. C., and Narang, H., 1972,Molec. Phys.,23,393; 1974,27,1393. The description of the reference fluid is improved by applying the modified Benedict-Webb-Rubin equation of state instead of the Verlet-Weis implementation of the Weeks-Chandler-Andersen perturbation scheme. Second virial coefficients predicted by perturbation theory to order μ4agree for Stock-mayer fluids with μ*2< 4 very well with exact values. Perturbation theory is capable of describing the low-density region of Stockmayer fluids with rather strong dipole moments. For these high values of the dipole moment, the Padé approximation of perturbation theory deviates significantly from the simulated coexistence curves in density and pressure. Compared with perturbation theory to order μ4, however, it is a far better approximation of the Stockmayer fluid coexistence curve. The behaviour of the Padé approximation in the critical region is not satisfactory.

ISSN:0026-8976    

DOI:10.1080/00268979300100231

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A dynamical viewpoint on the electronic system of a molecule is systematically introduced. It is shown that the conventional quantum-chemical consideration can be treated as a particular case of a more general approach connected with taking into account the time-dependence of molecular-orbital coefficients. Possible physical reasons for such a time-dependence are analysed. The Poincaré mapping for the collective electron dynamics in a molecule has been derived as a mapping of the idempotent matrix set into itself. Convergence conditions for this mapping as well as for the conventional Hartree-Fock selfconsistency procedure have been studied using the well-known fixed-point theorems. A possible physical significance of the divergence of Hartree-Fock selfconsistency procedure is discussed and some ways of extending the scope of the conventional quantum-chemical approaches are proposed.

ISSN:0026-8976    

DOI:10.1080/00268979300100241

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The density matrix of a spinI= 5/2 excited by a radiofrequency pulse is calculated. The interaction involved during the excitation of the spin system is first order quadrupolar. Consequently, the results are valid for any ratio of the quadrupolar coupling, θQto the pulse amplitude θRF. The behaviour of the central and the two satellite line intensities versus the pulse length is discussed. The aluminium nuclei (27Al) in a single crystal of corundum (Al2O3) are used to illustrate some results.

ISSN:0026-8976    

DOI:10.1080/00268979300100251

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Ab initiostudies are reported for the isomers HNCO, HOCN, HCNO, HONC, HNOC and HCON. The Møller-Plesset method (MP2) has been used to determine quadratic, cubic and quartic force constants in normal coordinates. As a result, both harmonic and anharmonic spectroscopic constants have been obtained, many of which are in good agreement with available experimental values. HCNO, fulminic acid, is a special case, being the classic four-atom quasilinear molecule. A full 6-dimensional potential surface has been obtained, and its low lying rovibrational levels have been calculated using the (6-dimensional) variational method. Good agreement with the principal features of the rovibrational spectrum has been obtained.

ISSN:0026-8976    

DOI:10.1080/00268979300100261

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The connection problem for asymptotic solutions on opposite sides of a parabolic potential well is analysed with the aid of theF-matrix method. A formula is obtained for theFmatrix connecting points on opposite sides of the well, and general properties of thisFmatrix are discussed. These properties apply also to more general, smooth single-well potentials.

ISSN:0026-8976    

DOI:10.1080/00268979300100271

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A full order parameter analysis has been carried out on a peptide plane of gramicidin A in aligned phospholipid bilayers. The most ordered molecular axis was determined to be the helical long axis of the molecule, possessing an order parameter of 0·93 ± 0·03 parallel to the bilayer normal, and an axial symmetry of -0·06 ± 0·04.

ISSN:0026-8976    

DOI:10.1080/00268979300100281

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Nonadiabatic dissociation energies are calculated for 619 vibration-rotation levels of the ground electronic state of HD+using a transformed Hamiltonian and an artificial-channels scattering method. In particular, coupling of rotational and electronic angular momenta is accounted for, so that levels with highNmay be studied. Relativistic and radiative corrections are added to give dissociation energies, from which calculated transition energies may be compared with the experimentally available values; the agreement is good, in most cases to within experimental error (0·001 cm-1).

ISSN:0026-8976    

DOI:10.1080/00268979300100291

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The clustering properties of sub-critical 3D Lennard-Jones particles have been determined by Monte Carlo computer simulation. The goal was to study liquid formation, which results in the definition of a cluster that is based on the radial distribution function of the LJ liquid. The cluster distribution was compared with that predicted by classical nucleation theory and analyzed with the cluster distribution scaling law. It was found that the surface tension must vary with cluster size in order for classical theory to fit the simulation data. Also, the scaling law was determined to have limited usefulness over the range of system densities and was most applicable to lower densities and higher temperatures. The density profile revealed that the clusters did not have well defined surfaces and were liquid-like in the interior. The fractal dimension was calculated from the radius of gyration and found to agree with the accepted value. The presence of a phase transition was determined from the cluster energy plots.

ISSN:0026-8976    

DOI:10.1080/00268979300100301

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor