ROTATIONAL LIFETIMES OF THE $B'^{2}\Delta$ STATE OF NO OBTAINED BY VUV LASER EXCITATION
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Date
1981
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Ohio State University
Abstract
The development of tunable coherent sources of vacuum ultraviolet radiation has opened new possibilities for high resolution spectroscopy in this region. Such a source, using resonantly-enhanced four-wave frequency mixing in Mg vapour, has been in operation for several years, in this laboratory. The coherent radiation $^{1}$ has a flux of $10^{10}$ photone in a pulse of 10 ns duration and is tunable from 1200 \AA to 1600 \AA in a narrow bandwidth $(\sim0.1 \mbox{cm}^{-1}$). In the present work, we report selective excitation of fluorescence from individual rotational levels of the $B^{\prime}^{2}\Delta state (\nu^{\prime} = 3,4,..., 8)$ of NO. Radiative lifetimes were measured at pressures from 10-1000 mtorr and extrapolated to zero pressure. For $\nu^{\prime}$ = 3,5 and 8 single exponential fluorescence decay was observed with an average lifetime of 220 $\pm10 ns.$ Levels $\nu^{\prime} = 1,6$ and 7, however, showed non-single exponential decay. The best fit of the data was obtained using a double exponential with resultant lifetimes of $220 \pm10 $ns and $30\pm 4 $ns. We attribute this behaviour to an interaction of the $B^{\prime}^{2}A (\nu = 4,6)$ levels with the $F^{2}\Delta$ state and of $B^{\prime}^{2}\Delta(\nu = 7)$ with the $N^{2}\Delta$ state.
Description
$^{1}$S.C. Wallace and G. Zdasiuk, Ap. Phys. Letters 28, 449 (1976): T.J. Mckee, B. P. Stoicheff, and S.C. Wallace, Opt. Letters 3, 207 (1978).
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