摘要:

Neutron diffraction measurements have been made on methyl alcohol at room temperature for an incident wavelength of 0·94 Å. Cross sections have been obtained for CD3OD, CD3OH, and mixtures of these compounds. These data are subtracted to obtain the separated structure factors for intermolecular H0H0, the hydroxyl components, and the non-hydroxyl components. The Fourier transformations of the structure factors show components of both intra- and intermolecular distribution functions. Width parameters obtained from model fits are too large for thermal vibrations and are interpreted as geometrical broadening due to the stretching of bonds, variations in bond angles, and rotation of the methyl group. Differences in the real space distribution function between hydrogen and deuterium are noted.

ISSN:0026-8976    

DOI:10.1080/00268978400102851

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Reactive scattering of Cl atoms with CH3I molecules has been studied over the range of initial translational energyE= 62-23 kJ mol-1, using a supersonic beam of Cl atoms seeded in He and Ne buffer gas. Laboratory angular and velocity distributions of ICl product were measured which indicate that reaction occurs via a long-lived collision complex with forward scattering appearing only at the highest collision energy. The dependence of the total reaction cross section on initial translational energy was also determined. The observed reactive scattering arises from an endoergic dissociation of the collision complex. The results are interpreted by a model which accounts for the effect of angular momentum conservation on this endoergic dissociation compared with the favoured dissociation of the complex back to reactants.

ISSN:0026-8976    

DOI:10.1080/00268978400102861

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Reactive scattering of Cl atoms with C2H5I molecules has been studied over the range of initial translational energyE= 63 - 24 kJ mol-1, using a supersonic beam of Cl atoms seeded in He and Ne buffer gas. Laboratory angular and velocity distributions of ICl product were measured which show that reaction proceeds via a long-lived collision complex at low initial translational energy. However at intermediate and higher initial translational energy, a forward scattered component emerges with a higher product translational energy than that of the long-lived complex component. This breakdown of long-lived complex dynamics occurs more readily in collisions at large impact parameters in contrast to the osculating complex model which assumes a statistical distribution of lifetimes independent of impact parameter.

ISSN:0026-8976    

DOI:10.1080/00268978400102871

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The parity-violating weak neutral current perturbation of the groundstate electronic energy has been calculated, byab initiomethods, for the (S)-isomer of hydrogen peroxide, over a range of standard Gaussian basis sets. The STO-N-31G, but not the STO-NG, sets give energy shiftsEpvwhich converge with increasingNtowards the correspondingEpvvalue given by an extended basis. Calculations for α-amino acids, peptides, model helical systems, with the STO-6-31G basis, or with an analogous set for corre-sponding sulphur analogues, show that theEpvshift is sensitive in sign and magnitude to the molecular conformation generally. It is found that L-alanine and the L-peptides in the α-helix and the β-sheet conformation have a lower ground state energy than the corresponding D-enantiomers due to the WNC interaction. The energy shiftEpvonly approximates to an expectedZ5proportionality, and it does not correlate consistently in sign with the handedness of a helical system.

ISSN:0026-8976    

DOI:10.1080/00268978400102881

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

We report a molecular dynamics study of the planar vapour-liquid interface for mixtures of Ar and Kr modelled by truncated Lennard-Jones potentials at 115·77 K and at two compositions. The simulations yield the density profiles, surface tension, surface of tension, adsorption, and normal and transverse components of the pressure tensor. Both the Irving-Kirkwood (IK) and Harasima (H) forms of the pressure tensor are calculated. The values of the surface tension calculated by the thermodynamic and mechanical (for both the IK and H pressure tensors) routes are in agreement, but the IK and H pressure tensors yield different values for the surface of tension, as expected. These results are compared with predictions of the mean field theory (MFT) of the interface. The agreement is generally good, the principal differences being due to the fact that the MFT predicts too low a liquid density. The MFT is also used to predict properties of the mixture interface for the full Lennard-Jones potential. For low concentrations of argon, the argon density profile is predicted to be weakly non-monotonic; this effect is larger for the full than for the truncated Lennard-Jones potential.

ISSN:0026-8976    

DOI:10.1080/00268978400102891

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The equilibrium geometry and harmonic vibrational frequencies have been predicted usingab initioSCF open shell methods for the2A″ ground state and the2A′ first excited electronic state of trifluoromethyperoxy radical, CF3OO. The frequencies are scaled to predict experimental values. The tentative assignment of the vibrational spectrum of the2A″ state given by Butler and Snelson is re-examined in the light of this study. Other spectroscopic features have been predicted for which there are no experimental observations at present.

ISSN:0026-8976    

DOI:10.1080/00268978400102901

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The dynamics of the non-rigid cyclopentene molecule have been studied by infrared and Raman spectroscopies. Even though, in the gas state, most of the rotation-vibration spectra exhibit complex structure due to the combinations of the internal vibrations with the ring-puckering mode, it is possible from the liquid state bandshapes to analyze the molecular rotational motion. In particular it is shown that this motion is quasi-diffusional with a diffusion tensor nearly spherical.

ISSN:0026-8976    

DOI:10.1080/00268978400102911

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The interaction-induced dipole correlation function for liquid CS2was calculated by molecular dynamics simulation. This correlation function was separated into components parallel and normal to the molecular symmetry axis, and the shape of these, as well as of the tensorialP2orientational correlation function, were calculated and compared. The discussion shows that we can obtain information on the environment anisotropy fluctuations contributing to the time dependence of the induced dipoles. The comparative discussion of several of these correlation functions can be useful in obtaining a differentiated, but still partial picture of the molecular dynamics in liquid CS2.

ISSN:0026-8976    

DOI:10.1080/00268978400102921

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Potential curves for trans- and cis-bending and C-C and C-H stretching vibrations in ground and singlet excited states of acetylene of both valence and Rydberg character are calculated using a large-scale MRD-CI approach. The energy surfaces obtained will be used for an interpretation of the U.V. spectrum of acetylene. The computed vertical energies for the lowest two transitionsÃ-[Xtilde]and[Btilde]-[Xtilde]are found to agree within 0·2 eV of the corresponding values reported experimentally.

ISSN:0026-8976    

DOI:10.1080/00268978400102931

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The triplet distribution function of the fluid with the square well potential is calculated to leading order in ρ by two methods: one is the method of generalized Fourier transform combined with the addition theorem of Bessel functions, and another is the geometrical method. The results are compared with those computed by the Monte Carlo and the molecular dynamics simulations. Higher order calculation by our scheme seems to be promising.

ISSN:0026-8976    

DOI:10.1080/00268978400102941

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor