LASER EXCITED FLUORESCENCE STUDIES OF THE PO RADICAL
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Date
1984
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Publisher
Ohio State University
Abstract
This paper reports preliminary results of laser fluorescence studies of the $A^{2}\Sigma^{+}\leftarrow X^{2}\pi (\sim 2500 {\AA})$ and $B^{2}\Sigma^{+}\leftarrow X^{2}\pi (\sim 3250 {\AA})$ transitions of PO. The PO is formed in a microwave discharge through a trace of dimethyl-methylphosphonate seeded into a flow of He or Ar carrier gas. PO fluorescence is excited downstream from the discharge region using a Nd:YAG pumped dye laser. Excitation and fluorescence scans have been performed in both electronic systems. The B-X scans agree well with earlier fluorescence $results.^{1,2}$ No previous laser fluorescence studies are available for the A-X system. This system was readily identified by comparison with previous uv absorption $studies.^{3}$ The B state lifetime, upon pumping in the $Q_{1}$ head of the (0,0) band, was found to be 260ns in excellent agreement with Ref. 1. A (rather crude) measurement of the quenching rate by $N_{2}$ is also in reasonable agreement with Ref. 1. Preliminary investigations indicate some dependence of lifetime on rotational level. The A state lifetime was $\sim 11.5ns$. This short lifetime is believed to be attributable to an extremely strong A-X transition. Quenching of both A and B states by He and Ar was found to be negligible for up to 10 torr of carrier gas.
Description
1. M.A.A. Clyne and M.C. Heaven, Chem. Phys. 58, 145 (1981). 2. W.R. Anderson, S.W. Bunte and A.J. Kotlar, Proceedings of the 1982 Chemical Systems Laboratory Scientific Conference on Chemical Defense Research, Special Publication ARCSL-SP-83030, June 1983. 3. K.P. Huber and G. Herzberg, Molecular Spectra and Molecular Structure, Van Nostrand Reinhold Co., New York, 1979 and references therein.
Author Institution: Ballistic Research Laboratory
Author Institution: Ballistic Research Laboratory