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Spectroscopy of SH (A-X) transition in Ar and Kr matrices: The caging of predissociation

Summary: Spectroscopy of SH (A-X) transition in Ar and Kr matrices: The caging
of predissociation
J. Zoval, D. Imre, and V. A. Apkariana)
Department of Chemistry, University of California, Irvine, California 92717
(Received 10 July 1992; accepted 15 September 1992)
The A(2E+)-X(211) transition of SH isolated in Ar and Kr matrices is studied by laser in-
duced fluorescence spectroscopy. The (O,O), ( l,O), and (2,O) transitions are observed in exci-
tation. These lines are structureless and homogeneously broadened (200-300 cm-`). The
(O,O), (0, 1>, and (0,2) emission bands, are strongly Stokes shifted and further broadened
( > 1000 cm-`). The spectra can be successfully interpreted in analogy with OH-Rg pair
interactions. The SH(A)-Rg potential is deeply bound ( - 1000 cm-' in Ar and -2000
cm -I in Kr) with nearly 1 A compression along this coordinate. FranckCondon analysis
indicates that the equilibrium bond length of SH(A) is 0.055 A longer than in the free radi-
cal. The A state, which is strongly predissociated in the free radical, relaxes radiatively in the
matrix: r=425 and 770 ns in Ar and Kr, respectively. Predissociation is treated as a two-
dimensional tunneling process between two electronic surfaces. Poor Franck-Condon factors
along the solvent coordinate, due to differential solvation of electronic states, leads to com-
plete arrest of electronic predissociation.
In the case of open shell, electronegative radicals,


Source: Apkarian, V. Ara - Department of Chemistry, University of California, Irvine


Collections: Chemistry