LASER ENHANCED COLLISIONAL EFFECTS IN THE MULTIPHOTON IONIZATION OF MOLECULES IN SUPERSONIC EXPANSIONS
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Date
1980
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Ohio State University
Abstract
Multiphoton ionization spectra of the $A^{2}\Sigma^{+}\leftarrow\leftarrow X^{2}\Pi_{1/2}$ state of supersonically cooled nitric oxide have been recorded. The results spectrum consists of three lines represenging the $\Delta N-0,1, \&2$ transitions. The rotational temperature is, therefore, less than 1K. At low laser powers the linewidths are limited by laser resolution $(< 0.1$ $cm^{-1})$, but at high laser powers the lines broaden drastically to the blue. This effect is temperature dependent also, in that the room temperature spectrum of NO does not show this effect. In this case only slight symmetrically broadening of the lines occurs when high laser powers are used. The casue of this broadening appears to be slow collisional interactions of the NO with helium carrier gas atoms. Recent theories of laser enhanced coillisionally promoted transitions predict the off-resonance creation of excited states as observed in these experiments.
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