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We report resonance-enhanced multiphoton ionization spectra of the isotopologues fluorobenzene h5 and fluorobenzene-d5. By making use of quantum chemical calculations, the changes in the wavenumber of the vibrational modes upon deuteration are examined. Additionally, the mixing of vibrational modes both between isotopologues and also between the two electronic states is discussed. The isotopic shifts lead to dramatic changes in the appearance of the spectrum as vibrations shift in and out of Fermi resonance. Assignments of the majority of the fluorobenzene-d5 observed bands are provided, aided by previous results on fluorobenzene-h5. [ABSTRACT FROM AUTHOR]

Examines the vibrational spectroscopy and intramolecular energy transfer in isocyanic acid (HNCO). Room temperature spectra; Strong intramolecular couplings that control the early stages of intramolecular vibrational energy redistribution; Consistency between the couplings and zero-order state separations with ab initio calculations of East, Johnson and Allen.

Examines the level mixing at the second CH stretch overtone state in benzene. Analysis of dynamic intramolecular vibrational redistribution characteristics; Involvement of vibrational level density in the vibrational mixing; Degree of localization of the CH stretch overtone vibrational system.

Presents a quantum mechanical description of vibrational motion in benzene in terms of vibrational coordinates and basis wavefunctions. Analysis of vibrational level mixing and intramolecular vibrational energy redistribution; Application of symmetrized local mode formalism; Treatment of remaining benzene vibrations as normal modes.

Focuses on the complete vibrational spectroscopy of pyrrole within the one-dimensional algebraic framework. Study of the carbon-hydrogen/nitrogen-hydrogen stretching levels including their possible anharmonic resonance mechanisms with other ring modes; Possible action of vibrational energy processes mechanisms on the molecules.

In this series, the characteristics of intramolecular vibrational-energy redistribution (IVR) present in the CH overtones of CHF3 are investigated. Particular attention is given to the multiple time scales and thus mechanisms present in the IVR dynamics. In Part I, a 9-dimensional ab initio potential energy surface is developed to adequately account for the vibrational couplings of all modes. Furthermore, all-mode vibrational state calculations, of large primitive space dimension, are performed using a recently developed wave operator sorting algorithm in tandem with the recursive residue generation method. All fundamentals, first overtones, and bimodal combination states with up to 3 quanta are presented. Also, the A1 and E-symmetry CH polyads are determined through the second overtone. Equilibrium geometry, rotational constants, and vibrational properties agree quantitatively with experiment in most cases. The error is systematic in origin and largely due to the error in the ab initio harmonic frequencies. New vibrational constants and resonance interactions are reported for the background modes. In contrast to the prominent CH stretch–bend Fermi resonance structure, responsible for ultrafast (t<50 fs) energy transfer, the CH polyads also exhibit vibrational fine structure of order 1 to 10 cm-1 due to background-mode coupling. This secondary coupling results in IVR on the picosecond time scale. © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR]