State selected unimolecular dissociation of HOCl near threshold: The 6νOH vibrational state

Abstract

State-to-state unimolecular reaction dynamics of HOCl near the dissociation threshold: The role of vibrations, rotations, and IVR probed by time-and eigenstate-resolved spectroscopy J. Chem. Phys. 111, 7359 (1999); 10.1063/1.480058Direct measurement of eigenstate-resolved unimolecular dissociation rates of HOCI The spectroscopy and unimolecular dissociation dynamics of HOCl are examined by accessing rotational resonances of the 6 OH vibrational level over the K a ϭ0 -5 manifolds using overtoneovertone double resonance. The spectroscopic analysis indicates that state mixing between the zeroth-order ''bright'' O-H stretching overtone state, 6 0 0, and ''dark'' background vibrational levels is incomplete as the bright state couples to only a fraction of the available states. The coupling of 6 0 0 to a set of nearby dark states is mediated primarily by anharmonic coupling with the fourth-order vibrational resonance k 1,223 playing a particularly important role through its ability to couple the 6 0 0 state directly to the 5 2 1 vibration and indirectly to the 4 4 2 vibration. The measured state-specific unimolecular dissociation rates for 6 0 0 show large fluctuations with J and K a and are substantially slower than that expected on the basis of statistical theory. The rate fluctuations are interpreted on the basis of spectroscopic data which suggest that the fluctuations arise as a result of variation in state mixing as different dark vibrational states come in and out of resonance with the bright state for different values of J and K a .

Relative vibrational overtone intensity of cis–cis and trans–perp peroxynitrous acid

“…21 Briefly, the photolysis chamber consists of a glass cell equipped with a viewing window for monitoring laserinduced fluorescence ͑LIF͒, two sets of mutually orthogonal side arms for introducing laser light, and several inlet ports for adding reagents and monitoring pressure. The inside of the cell is coated with halocarbon wax to minimize sample wall loss.…”

Dynamics and spectroscopy of vibrational overtone excited glyoxylic acid and 2,2-dihydroxyacetic acid in the gas-phase

“…2,4,5,25 While examples of bond and mode selective chemistry proved elusive, a few systems have been investigated where intramolecular vibrational redistribution ͑IVR͒ is slow compared with unimolecular reaction and consequently "nonstatistical" mode selective behavior could be observed. 1,10,12,[26][27][28][29][30][31][32][33][34][35][36] The light initiated vibrational overtone pumping of GA adds an interesting example to the pyruvic acid ͑PA͒ chemistry where very fast reaction occurs by direct dynamics. 1,37 The Sun is the driving force in atmospheric chemistry and therefore fundamental studies of photoreaction dynamics are of paramount importance in this field.…”

Highly Excited Motion in Molecules: Saddle-Node Bifurcations and Their Fingerprints in Vibrational Spectra

“…Spectroscopic information for HOCl, the other cornerstone of this article, is much sparser. 42,43 For technical reasons only states with large excitations of the OH stretch have been analyzed experimentally; although these states are very interesting for investigating the dissociation of HOCl, [44][45][46] they exhibit a clear local-mode behavior and therefore are not relevant for the topic of this article. Although HOBr behaves much like HOCl, there are distinct differences.…”