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In the static field limit, the vibrational hyperpolarizability consists of two contributions due to: ~1! the shift in the equilibrium geometry ~known as nuclear relaxation!, and ~2! the change in the shape of the potential energy surface ~known as curvature!. Simple finite field methods have previously been developed for evaluating these static field contributions and also for determining the e...

Reaction paths and classical and quantum trajectories are studied within a generalized HamiltonJacobi framework, which allows to put on equal footing topology and dynamics in chemical reactivity problems. In doing so, we show how high-dimensional problems could be dealt with by means of Carathéodory plots or how trajectory-based quantum-classical analyses reveal unexpected discrepancies. As a w...

Ab inido molecular orbital ealenlations with large, polarizetion basis sets and incorporating valence electron correlation have been employed to examine the [GHzO]+' potential energy snrface. Four [WzO1+' isomers have been identified as potentially stable, observable ions. T h e are the experimentdly well-known ketene radical cation, [CH4=0 ]+ ' (a), and tbe presently unlmown ethynol radical ca...

Methods: Following upon the work presented in Ref. [1], quadrupole-constrained Hartree-Fock calculations are used to create a potential energy surface. An isomeric state and a state beyond the second barrier peak are excited by means of instantaneous as well as temporally extended gauge boosts with quadrupole shapes. The subsequent deexcitation is studied in a time-dependent Hartree-Fock simula...

The H, system has excited much mterest both theoretically [l] and experimentally [2]. In particular It has been used to study elastic, inelastic and reacttve scattermg. The H3 molecule has been observed in an excited Rydberg state [3], a Bndtng confirmed by ab initio calculation [4,5], but as yet we know of no experimental evidence for it in its electronrc ground state. The ground-state potenti...

The nuclear Franck-Condon factor for the photodetachment processes H(D)2F-+h~+H (D)2+Fte-, H(D)FtH(D) tefor J=O has been calculated using the S-matrix Kohn variational method for reactive scattering on the T5a potential energy surface. The positions of peaks in the spectra of our theoretical calculations are in excellent agreement with those found in the recent experiment of Weaver and Neumark....

Molecular reaction dynamics in the adiabatic representation is complicated by the existence of conical intersections and the associated geometric phase effect. The first-derivative coupling vector between the corresponding electronically adiabatic states can, in general, be decomposed into longitudinal ~removable! and transverse ~nonremovable! parts. At intersection geometries, the longitudinal...

We present cross sections for rotational, vibrational, and fine-structure transitions in He–CaH(S) collisions at cold and ultracold temperatures calculated using the ab initio potential energy surface reported in the preceding paper. Rotational quenching is fast, vibrational quenching is slow. The spin-rotational interaction, although small and having no influence at temperatures above 10 K, ch...

The importance of rotational transition rates in the analysis of cold interstellar clouds is well known. We present results, for temperatures ranging from 5 to 80 K, for the hyperfine-resolved rotational transitions of DCO+ induced by collision with helium. Since the isotopic substitution is not expected to introduce significant changes, close-coupling calculations are based on a potential ener...