Distribution of internal states of CO from O ( 1D) + CO determined with time-resolved fourier transform spectroscopy

Hui Fen Chen, Yuan-Pern Lee*

*Corresponding author for this work

Research output: Contribution to journalArticle

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Following collisions of O ( 1D) with CO, rotationally resolved emission spectra of CO (1 ≤ v ≤ 6) in the spectral region 1800-2350 cm -1 were detected with a step-scan Fourier transform spectrometer. O ( 1D) was produced by photolysis of O 3 with light from a KrF excimer laser at 248 nm. Upon irradiation of a flowing mixture of O 3 (0.016 Torr) and CO (0.058 Torr), emission of CO (v ≤ 6) increases with time, reaches a maximum ∼10 μs. At the earliest applicable period (2-3 μs), the rotational distribution of CO is not Boltzmann; it may be approximately described with a bimodal distribution corresponding to temperatures ∼8000 and ∼500 K, with the proportion of these two components varying with the vibrational level. A short extrapolation from data in the period 2-6 μs leads to a nascent rotational temperature of ∼10170 ± 600 K for v = 1 and ∼1400 ± 40 K for v = 6, with an average rotational energy of 33 ± 6 kJ mol -1. Absorption by CO (v = 0) in the system interfered with population of low J levels of CO (v = 1). The observed vibrational distribution of (v = 2):(v = 3):(v = 4):(v = 5):(v = 6)= 1.00:0.64:0.51:0.32:0.16 corresponds to a vibrational temperature of 6850 ± 750 K. An average vibrational energy of 40 ± 4 kJ mol -1 is derived based on the observed population of CO (2 ≤ v ≤ 6) and estimates of the population of CO (v = 0, 1, and 7) by extrapolation. The observed rotational distributions of CO (1 ≤ v ≤ 3) are consistent with results of previous experiments and trajectory calculations; data for CO (4 ≤ v ≤ 6) are new.

Original languageEnglish
Pages (from-to)12096-12102
Number of pages7
JournalJournal of Physical Chemistry A
Issue number44
StatePublished - 9 Nov 2006

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