摘要:

A new crossed beam instrument for the investigation of ion-molecule reactions is described. The reaction CO++O2→CO2++O has been studied over the range of initial relative translational energies from 1·8 to 10 eV. The cross-section increases as the energy is raised to 5 eV and then decreases as the energy is increased further. The reaction proceeds by a direct mechanism at all energies, though at low energies there are substantial interactions between all four atoms. As the initial energy is raised the mechanism becomes more impulsive and there is evidence for the formation of products in an excited electronic state.

ISSN:0026-8976    

DOI:10.1080/00268978000100691

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Quantum mechanical reaction probabilities are reported for the collinear reaction F+H2(v)→FH(v′)+H in an energy range where two or three vibrational H2statesvare open. Rotated Morse-cubic spline representations of the extended LEPS surfaces MuckermanIandV, and an adaptation of the BOPS SCFCI surface have been used. The scattering is dominated by resonances. A detailed investigation of the different kinds of resonance behaviour is presented. For the two LEPS surfaces, overall features of the reaction probability curves can be correlated qualitatively in a one-to-one manner. Differences between the BOPS and LEPS reaction probabilities are more pronounced forv=1 than forv=0. For all surfaces, effects of vibrational excitation show a much more systematic behaviour in terms of the reverse reaction than for the forward reaction. A multi-step mechanism is deduced for the reaction, and an attempt is made to give an interpretation in terms of physical concepts including centrifugal effects, Franck-Condon transitions and quasibound states. No obvious simple trends emerge from a surprisal analysis. Most surprisal plots are markedly non-linear in the energy range considered.

ISSN:0026-8976    

DOI:10.1080/00268978000100701

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The microwave and radiofrequency Stark spectra of four isotopic species of the weakly bound complex argon-hydrogen bromide (Ar · H79Br, Ar · H81Br, Ar · D79Br, Ar · D81Br) have been studied using the technique of molecular beam electric resonance spectroscopy. Only transitions within the ground vibrational state have been observed.

ISSN:0026-8976    

DOI:10.1080/00268978000100711

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

We show that the Newton-Raphson method recently developed for solving the liquid-structure integral equations can be used to solve the hypernetted chain equation for two-component ionic systems. The characteristics of the new method are studied by applying it to a model ionic system for a range of thermodynamic states spanning the aqueous solution and molten salt régimes. We find that its stability and rate of convergence are much superior to those of the usual method. There is a region of thermodynamic states in which the method fails to produce solutions. However, our results indicate that this is the region bounded by the spinodal line, within which the hypernetted chain equation possesses no physical solutions.

ISSN:0026-8976    

DOI:10.1080/00268978000100721

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

A group of two-parameter intramolecular distributions for degenerate vibrations has been investigated. The distributions are of physical significance in calculating electronic transitions and have certain important properties which are formulated in terms of addition theorems.

ISSN:0026-8976    

DOI:10.1080/00268978000100731

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

We derive a theory of inter- and intramolecular transfer of vibrational, rotational and translational energy in collisions of polyatomic molecules, in the case that only short range forces are important. Normal mode vibrations of molecules are treated quantum mechanically whereas translations and rotations are assumed to be classical degrees of freedom. We are able to show that, in case of short range forces, the energy exchange in binary collisions is essentially governed by an effective mass which is given by an algebraic function of the usual reduced mass and moments of inertia and depends also on the relative orientation of the two molecules. As an application of the theory, we calculated the probabilities for collision-induced 1 →0 transitions of thev3mode in pure CH3I, CH3Br and CH3Cl gases. The calculated values are close to the experimental vibrational deactivation probabilities.

ISSN:0026-8976    

DOI:10.1080/00268978000100741

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

When a solution of a porphin inn-octane is slowly frozen the guests predominantly occupy a single site (A) in which the porphin has been shown to replace a number of host molecules displaced along theb-direction; if the solution is quickly frozen the optical spectra reveal the presence of a second site (B). In the present paper it is shown that the occurrence of these two types of sites,AandB, is a common phenomenon throughout the series fromn-heptane (C7) ton-decane (C10) as hosts and phenomenological criteria are formulated to distinguish between the two kinds of sites.

ISSN:0026-8976    

DOI:10.1080/00268978000100751

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Force constants and dipole moment derivatives have been computed for the molecules CH3X(X=F, Cl, Br, I) using MO wavefunctions with pseudo-potentials for the interaction between the inner shell and valence electrons. The values obtained at the SCF approximation level from a set of gaussian valence orbitals contracted in double-zeta form and enriched with polarization functions compare well with experimental assignments of force and interaction constants, as well as integrated intensities from infrared data. The transferability of atomic force fields and polar tensors (second derivatives of total energies and first derivatives of dipole moments with respect to atomic displacements in cartesian coordinates) is discussed.

ISSN:0026-8976    

DOI:10.1080/00268978000100761

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

A simple semiempirical approximation previously proposed for the isotropic intermolecular forces between two closed shell systems is tested in detail for the argon-argon interaction. The potential is based on the knowledge of the first-order coulomb interaction energy, a suitably damped three term long range asymptotic expansion of the second order coulomb energy, and a semiempirical representation of the exchange interaction energy which contains one adjustable parameter. The single adjustable parameter can be reliably determined by fitting the second virial coefficient for argon in the 130–773 K temperature range with the long range interaction coefficients being constrained within the theoretical bounds specified by Tang, Norbeck and Certain. The reliability of the potential is compared with that of several literature potentials by comparing the theoretical predictions obtained from the potentials with experimental results for the second virial coefficient, viscosity, thermal conductivity and thermal diffusion ratios for dilute argon gas, and with spectroscopic data for the dimer, and with SCF calculations of the Ar-Ar potential at small interatomic separations. Our best potential predicts these properties with a precision as good as or better than other recent potentials which generally contain more adjustable parameters and/or involve more input data. The results confirm earlier work that suggested that the scheme tested is capable of yielding reliable isotropic potentials for the interaction of closed shell systems for 0·3 ≲R/Rm⩽ ∞ whereRmis the intermolecular distance at the van der Waals minimum. The scheme appears to offer a method for obtaining reliable potentials while avoiding problems associated with optimizing many parameters with respect to fitting experimental constraints.

ISSN:0026-8976    

DOI:10.1080/00268978000100771

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

A comparison is made between the rotovibrational Raman bands of fluid nitrogen at room temperature in the 180–355 amagat density range and the corresponding pure rotational bands reported previously. Accurate moment values are derived from the Raman spectra, accounting for the response of the entire experimental apparatus, after subtraction of the unwanted isotope band and of the leaking polarizedQbranch. Correlation times are also calculated for both rotovibrational and pure rotational spectra accounting for the finite instrumental slitwidth.

ISSN:0026-8976    

DOI:10.1080/00268978000100781

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor