15min:

AMY BURROUGHS AND MICHAEL C. HEAVEN, Department of Chemistry, Emory University, Atlanta, GA 30322.

~~~~~~We have investigated the properties of matrix isolated CD and present a comparison with earlier studies of the CH radical. The CH/D radicals were formed by the microwave dissociation of methane. The products were trapped in solid Ar or Kr at 12 K and investigated using laser excitation and dispersed fluorescence techniques. The B^{2 -}-X² and A² -X^ 2 transitions were studied. The decay of CH(B) v~=~0 is primarily radiative in both Ar and Kr with small contributions from B A nonradiative transfer. Fluorescence was not detected from CD(B), v~=~0, as the B A transfer process was much faster than radiative decay for this isotope. Differences in the B A energy gaps are responsible for the large difference in the transfer rates of the two isotopes.

~~~~~Excitation spectra yield evidence that CH/D(B) rotates in solid Ar and Kr matrices. Low frequency structure in the B-X (0,0) absorption band changed considerably on H/D isotopic substitution while it was relatively insensitive to the replacement of the matrix material. Absorption spectra for the A-X transition did not show evidence for rotation in the matrix, but it is likely that optical selection rules prevent the observation of rotational structure in this instance.

~~~~~Vibrational relaxation of CH/D(B) is faster for the heavier isotope, indicating that vibration to rotation energy transfer is the dominant relaxation mechanism.

Work supported by the National Science Foundation