DISTRIBUTION OF INTERNAL STATES OF CO AND OH FROM O($^{1}$D) + C$_6$H$_6$ AND C$_6$D$_6$ DETERMINED WITH TIME-RESOLVED FOURIER-TRANSFORM SPECTROSCOPY
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Date
2008
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Ohio State University
Abstract
Rotationally resolved infrared emission spectra of CO ($1\leq v \leq 6$) in the spectral region 1800 -- 2350 cm$^{-1}$ and OH ($1\leq v \leq 3$) in the region 2800 -- 3700 cm$^{-1}$ were recorded with a step-scan Fourier-transform spectrometer. CO shows a rotational distribution corresponding approximately to temperatures 1520 K for $v$ = 1 and 860 K for $v$ = 2 -- 6, with an average rotational energy of $9\pm1$ kJ mol$^{-1}$ at the earliest applicable period (2.5 -- 7.5 $\mu$s) upon photolysis. Extrapolation to time zero based on data in the range 2.5 -- 27.5 $\mu$s yields an average nascent rotational energy of $14\pm4$ kJ mol$^{-1}$. Observed vibrational distribution of CO corresponds to a vibrational temperature of $5800\pm330$ K and an average vibrational energy of $33\pm3$ kJ mol$^{-1}$. OH shows a rotational distribution corresponding to temperatures 550 K for the P1 branch ($v$ = 1 -- 3) and 620 K for the P2 branch ($v$ = 1 -- 3), with an average nascent rotational energy of $4\pm1$ kJ mol$^{-1}$. The observed vibrational temperature of OH is $4830\pm230$ K, corresponding to an average vibrational energy of $21\pm4$ kJ mol$^{-1}$. The branching ratio of [CO]/[OH] is $2.1\pm0.1$ for O ($^{1}$D) + C$_6$H$_6$ and no OD was observed from O ($^{1}$D) + C$_6$D$_6$. The significant deuterium isotope effect will be discussed.
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Author Institution: National Tsing Hua University, Departmeny of Chemistry, Hsinchu 30013, Taiwan; National Chiao Tung University, Department of Applied Chemistry, Hsinchu 30010, Taiwan, and Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan