Maximum extinction coefficients and ascLUator strength were measured for several CHZ and CH3 trax Lions in the vacuum W. The method employed involved in the vacuum W flash photoIysIs of keteae and diazomethane and vacuum W s~c~ophoto~stry.
Knowledge of the values of ~so~tion cross sectious of molecular transient Species is important for theoretical and experimental applications. In particular, these data are essential in making accurate measurements of concentxations of short-lived molecular fragments. Rydberg transitions for most molecules occur in the vacuum ultraviolet region of the spechvm and the cross sections are typically large_ Thus very low detection limits can be achieved by utilizing these vacuum UV absorptiona.
In this work flash photolysis has been used to produce known concentrations of methylene and methyl radicals. From absorption measurements, utilizing kinetic spectroscopy in the vacuum ultraviolet, the oscillator strengths were determined for CZiz at 141.5 nm and CBS at 150 nm. The experimentti details have been previously described 111. Samples of diazometh.a.ne and of ketene were photolgsed in their strongest absorption continua and the fractional decompositions of carefully prepared samples of these two compounds were measured by means of plate photometry. Endproduct measurements revealed that the major fraction of the decomposed parent compounds yielded singlet methylene. This state could be quantitatively quenched to the triplet state by the addition of an inert gas. Alternatively, added molecular hydrogen quantitatively converted singlet methylene into methyl radicals. Thus the vacuum ultraviolet absorption Spectra of the Rydberg transitions of both methylene and methyl radicals couId be directly monitored. * visiting scientist, Physical Chemistry Division,