The unimolecular dissociation of HCO: A spectroscopic study of resonance energies and widths

Abstract

Articles you may be interested inThe unimolecular dissociation of HCO. II. Comparison of calculated resonance energies and widths with high resolution spectroscopic data Theoretical stabilization and scattering studies of resonances in the addition reaction H+CO = HCO J. Chem. Phys. 94, 4192 (1991); 10.1063/1.460652Collision energy dependence of Penning ionization electron spectra in crossed supersonic beams: He*(21S)+N2We use dispersed fluorescence ͑DF͒ and stimulated emission pumping ͑SEP͒ spectroscopies on the B 2 AЈ -X 2 AЈ system of jet-cooled HCO to measure the vibrational energies, resonance widths, and relative fluorescence intensities of 73 bound and resonance states supported by the ground-state potential energy surface. The SEP experiments use both two-color resonant four-wave mixing ͑RFWM-SEP͒ and the more conventional technique in which SEP signals are obtained from fluorescence depletion ͑FD-SEP͒. Where applicable, RFWM-SEP provides superior spectra to those obtained with FD-SEP, which is susceptible to saturation broadening that can prevent accurate determinations of resonance widths. The observed bound and resonance states span an energy range of 2000-21 000 cm Ϫ1 and comprise a wide range of vibrational excitation among the three vibrational modes, including states with 1-12 quanta of excitation in the C-O stretch, 0-5 quanta of bending excitation, and 0-1 quanta of excitation in the C-H stretch. The widths are markedly mode-specific and often display striking, nonmonotonic variations with increasing C-O stretch excitation. We compare our results to those of previous DF and SEP studies and to recent dynamical calculations of resonance energies and widths that use realistic potential surfaces derived from ab initio calculations. The resonance widths are particularly sensitive gauges of the unimolecular dissociation dynamics and provide stringent tests of theoretical potential surfaces.

Rotational analysis of the HCO and bands

“…The vibrational origin of theX (0, 0, 2) level was obtained from the vibronic origin of theBð0; 0; 1Þ state deduced above, subtracted from the band origin of the 3 1 2 electronic transition. The vibrational origin ofX ð0; 0; 2Þ, 2140.60 ± 0.4 cm À1 , obtained by the LIF spectra in this work is consistent with the value of 2142 cm À1 determined from the dispersed fluorescence and stimulated emission pumping spectroscopy [34]. The fitted rotational constant, A = 29.2 ± 0.08 cm À1 is larger than the values for the (0, 0, 0) and the (0, 0, 1) states.…”

Elementary reactions of formyl (HCO) radical studied by laser photolysis—transient absorption spectroscopy

“…Due to relatively weak C-H bond and large vibrational frequencies, the radical has isolated resonances at energies above the dissociation threshold. These resonances have been extensively studied both using spectroscopic techniques and theoretically [4][5][6][7][8][9]. This feature is expected to have a significant impact on the pressure fall-off curve for reaction (1) [10].…”

Rotational effects in six-dimensional quantum dynamics for reaction of H2 on Cu(100)

“…8 These attributes have led to successful application of TC-RFWM to the study of numerous stable and transient species. [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] Diagrammatic perturbation theory ͑DPT͒ has proven to be a very effective tool in analyzing the spectra obtained in gas-phase TC-RFWM. Analytic expressions for the signal line profile have been reported for a variety of TC-RFWM schemes used in double-resonance spectroscopy of bound 23 and quasibound 24 molecular states.…”