LASER-INDUCED FLUORESCENCE OF HCO RADICAL.
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Date
1986
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Ohio State University
Abstract
Laser-induced fluorescence from the $(0.90^{\circ})$ level of the $\tilde{A}^{2}\Pi A^{\prime\prime}$ state of the HCO radical has been detected following pulsed dye laser excitation of the (0,0,0) level of the $\tilde{X}^{2}A^{\prime}$ state at 614.48nm. Fluoroescence emission from $\widetilde{A}{^{2}}\pi A^{\prime\prime} HCO$ is extremely weak, due to the predissociation of all levels with $1^{\prime} > 0$. The HCO is generated by the photolysis of a 0.2 to 25 torr sample of acetaldehyde vapr at 300k using the 308 nm output of a XeCl excimer laser. Fluorescence excitation and dispersed emission spectra of $Lademann^{1}$ is not observed. A determination was made of the vibrational frequency of the C-H stretch, $V_{1}^{\prime\prime} = 2432 cm^{-1} + 20 cm^{-1}$ for the first time in the gas phase, and it is close to the value of $2483 cm^{-1}$ determined in an Ar $matrix.^{2}$ The fluorescence lifetime of $\widetilde{A}^{2}\pi A^{\prime\prime} HCO$ was measured to be $<15$ nsec, and is shorter than the 46 nsec lifetime reported by Konig and $lademann.^{1}$. The disappearance kinetics of the HCO radical was observed to be second-order in HCO.
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$^{1)}$ R. Konig and J. Lademann, Chem. Phys. Lett., 94, 152 (1983). $^{2)}$ D. E. Milligan and M. E. Jacox, J. Chem, Phys., 41, 3032 (1964) Address of Stone: Department of Chemistry, San Jose State University, San Jose, CA. 95192 Address of Noble: Department of Chemistry, University of Southern California, Los Angeles, Address of Lee: Department of Chemistry, University of California, Irvine, CA 92717
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