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An exact analysis of coupled coherent state (CCS) theory in the moving locally quadratic Hamiltonian approximation is shown to reproduce both the linearized coherent state matrix element of the Herman-Kluk propagator and the coherent state overlap with Heller's thawed Gaussian wave function. The derivation is applicable to anharmonic as well as harmonic systems, because the quadratic approximation is taken to apply only in the vicinity of a particular classical trajectory. New compact expressions for the linearized Herman-Kluk coherent state matrix element are given, and improvements for the practical application of CCS theory are discussed. [ABSTRACT FROM AUTHOR]

The experimental and theoretical lifetimes for rovibronic k ³Π[sup -, sub u] states of H[sub 2] and D[sub 2] isotopomers have been investigated over a wide range of vibrational v′ and rotational N′ quantum numbers. Lifetimes have been measured by a delayed coincidence method, combined with direct electron-impact excitation of the ground state molecules and single photon counting techniques to detect induced fluorescence to the a ³&Zigma;[sup +, sub g] state. Pronounced pressure-dependence of the experimental lifetimes was observed and properly taken into account. The pure radiative lifetimes of the k ³Π[sup -, sub u] states were estimated using theoretical transition dipole moments responsible for the visible k ³&:Pi;[sub u] → a ³&Zigma;[sup +, sub g] transition plus infrared emission on the higher-lying ³Γ[sub g] states belonging to the 3s,d ³ Γ[sub g] complex. Both the predissociative and autoionization decay rates were predicted by the Fermi-Golden rule based on radial coupling matrix elements for the k ³Γ[sub u] ∼ sup3;Π[sub u] and k ³Π[sub u] ∼ X² &Zigma;[sup +, sub g] (H[sup +, sub 2]) pairs of interacting states, respectively. The required electronic matrix elements as a function of internuclear distance R were derived in the framework of quantum-defect theory modified to allow explicit consideration of regular radial coupling effects. The relevant quantum-defect functions of all states treated were extracted from published highly accurate BornOppenheimer potential curves. Both the total theoretical radiative, predissociative plus autoionization rates and the calculated rovibronic term values agree well with their experimental counterparts. The N′-dependence of the experimental and theoretical lifetimes is found to be negligible for both isotopomers while a pronounced v′-dependence is observed for a H[sub 2] isotopomer. The vibrational... [ABSTRACT FROM AUTHOR]

The multichannel quantum defect theory of rotational–electronic channel interactions and spectroscopic absorption intensities for rigid asymmetric tops is described. The symmetry selection rules are given in terms of the overall rotational–electronic parity and the even or odd character of K+a=Ka-λ. The angular momentum recoupling from Hund’s case (b) to (d) is shown to be accompanied by increasingly strong propensity rules K+a=|K‘a-λ‘| and |N+-J‘|≤l‘, which explain the simplicity of the rotationally resolved photoionization spectra of H2O and D2O without recourse to any predissociation mechanism. The main features of this spectrum are well reproduced, and ionization limits of 101 772(2) and 101 920(5) cm-1 are derived for H2O and D2O. [ABSTRACT FROM AUTHOR]