摘要:

Tetrafluoromethane gas depolarized scattering has been recorded at 294·5 K and 20·3 amagat in the frequency range 2-340 cm−1. Two-body depolarized scattered intensities have been measured in absolute units up to 150 cm−1. The theoretical intensities taking into account multipolar polarizabilities and several hyperpolarizability contributions have been calculated. From comparison with experiment, the independent components of the dipole-quadrupole and the dipole-octopole polarizability tensors have been estimated and checked with recentab initiotheoretical values.

ISSN:0026-8976    

DOI:10.1080/002689797172633

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Multiphoton optical rotation of uridine and sucrose has been measured at 308 nm. The signature of the multiphoton nature of the rotation is its dependence on intensity, being proportional toIN−1, whereNis the number of photons involved in the forward scattering event. In uridine, a specific two-photon rotation of −0·7±0·1 was measured for 50 mW laser power, while for sucrose at the same power level the specific two-photon rotation was found to be −0·16±0·05.

ISSN:0026-8976    

DOI:10.1080/002689797172642

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The structures of ion clusters have been investigated for the restricted primitive model in the low density limit. The calculations have been accomplished by a Monte Carlo integration over the probability function of the cluster configuration. The size of the clusters ranges from dimer to octamer. Properties related to the structure, such as the number of associating bonds, the cluster volumes and the multipole moments including ion polarizability, have been calculated. Two qualitatively different approaches for the Bjerrum distance have been investigated and compared with respect to its physical relevance. The Bjerrum distance is the crucial and arbitrary parameter in the ion cluster theory. As a result it was found that a considerable small constant Bjerrum distance is superior to Bjerrum's original temperature dependent approach.

ISSN:0026-8976    

DOI:10.1080/002689797172651

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Temperature dependent molecular properties have been calculated using a combination of classical molecular dynamics and Monte Carlo methods and semiempirical quantum techniques. Sample geometries from stochastic dynamics and Metropolis Monte Carlo calculations have been fed into the AM1 Hamiltonian in MOPAC-5 to produce estimates of dipole moments, polarizabilities and hyperpolarizabilities at a variety of temperatures for the molecules butane, 4-cyanoaniline, dopamine (3,4-dihydroxyphenylethylamine) and 1,2-di-(4-cyanophenyl)ethane. Reasonably reliable results can be produced with only a modest use of computer time.

ISSN:0026-8976    

DOI:10.1080/002689797172660

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Osmosis has been studied using the methods of molecular dynamics and for several different models of a semi-permeable barrier. One of these models has also been used in theoretical and Monte Carlo investigations of the effect of such a barrier on the structure of a hard sphere fluid (Marsh, P., Rickayzen, G., and Calleja, M., 1995,Molec. Phys., 84, 799 ; Kim, S.-C., Calleja, M., and Rickayzen, G., 1995,J. Phys.:condens. Matter, 7, 8053). Results presented in these papers showed that this problem also provides a sensitive test for the validity of various density functional theories. In order to bring the theory to bear on the problem of osmosis, this earlier study is extended to the hard core Lennard-Jones fluid. At the same time a new sum rule for the density of a fluid in a periodic potential, which provides a useful check on the computations, is derived. It is again found that the agreement between the computed and the simulated density profiles is good except at the centre of the barrier and when the bulk density and pressure are close to the critical.

ISSN:0026-8976    

DOI:10.1080/002689797172679

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

XH-stretching vibrational band intensities have been calculated for seven small molecules with OH, NH and CH bonds, respectively, using the simple harmonically coupled anharmonic oscillator local mode model andab initiodipole moment functions, both expressed in XH-stretching bond coordinates. The dipole moment functions were calculated with a triple valence basis set including both diffuse and multiple polarization functions, and at different levels ofab initiotheory. The self-consistent field Hartree-Fock calculation is compared with different ways of including electron correlation. These calculations show that in general electron correlation in the ab initio calculation of the dipole moment function is often important in predictions of fundamental XH-stretching band intensities, whereas the XH-stretching overtone intensities are insensitive to electron correlation. This insight is important for studies of larger molecules where the highest levels of theory are not computationally feasible.

ISSN:0026-8976    

DOI:10.1080/002689797172688

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The previously established general solution of the Ornstein-Zernike (OZ) equation is elaborated upon further. A systematic and consistent summary of the first-order OZ solutions for various types of potentials is made, which enables one to obtain the first-order radial distribution function (RDF) rapidly. Typical potentials, including the hard sphere, sticky hard sphere, Yukawa, square-well, Lennard-Jones and Kihara, are treated with emphasis in this work. A new approach for obtaining explicit RDF expressions is proposed. Established on a basic functionB(n1,n2,n3,i,a), it is capable of representing the explicit expressions in a compact and consistent manner for all the potentials mentioned above. Moreover, the proposed approach can yield RDF values directly in any number of shells corresponding to anyrvalues. The resulting expressions can be programmed readily in a computer thus facilitating the RDF computation.

ISSN:0026-8976    

DOI:10.1080/002689797172697

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Single vibronic level fluorescence spectra of bands in the 31120-32160 cm−1region of SO2were measured under low rotational temperature conditions in an expanded supersonic jet. Eight weak bands were confirmed as belonging to the34S16O2system : their resonance vibrational transitions were found to match the term energies of this isotope. The correlating bands in the32S16O2system were identified by noting that the Franck-Condon patterns of their dispersed fluorescence spectra were similar to those of the34S16O2bands. The analysis of the spectra also concludes that some of the weak bands in the above region can be due to32S16O2bands whose upper levels have Bev2= Be2× av1vibronic symmetry.

ISSN:0026-8976    

DOI:10.1080/002689797172705

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The molecular motions associated with different phase transformations in the solid state of 1-cyanoadamantane have been studied by thermally stimulated discharge current technique (TSDC) and the obtained results were compared with those obtained by other techniques namely differential scanning calorimetry, nuclear magnetic resonance and dielectric relaxation spectroscopy. The transformations glassy phase (Ig) → plastic metastable (I'), plastic metastable (I') → brittle (II) and brittle (II) → plastic stable (I) were analysed and the obtained results confirmed the TSDC technique as a powerful tool to study order-disorder transitions in molecular crystals. g

ISSN:0026-8976    

DOI:10.1080/002689797172714

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Computer simulations are used to investigate the recent prediction (R. van Roij et al., 1995, Phys. Rev., E52, R1277) of transverse interlayer order in the smectic-A phase of hard spherocylinders. For short rods, and close to the melting point of the smectic-A phase, a fraction of about one per cent of the particles are in the transverse interlayer state. For longer rods and further away from the melting transition a much lower fraction is found. Possible implications for interlayer diffusion and end-over-end rotational diffusion are discussed.

ISSN:0026-8976    

DOI:10.1080/002689797172723

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor