Infrared multiphoton dissociation of SF6 at long wavelengths

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Abstract
The dissociation probability Pd of 32 SF6 was investigated between 908 and 875 cm−1 at room temperature and at 140 K. In the region of the expected Pd maximum of 36SF6 (≊905 cm−1), we found a ten times higher Pd(32) (implying a ten times smaller selectivity for 36S) than expected from extrapolation of shorter wavelength data. The Pd spectrum in this and in other regions point to an important role of direct multiphoton transitions to levels containing quanta of the neighboring combination mode ν5+ν6 (870 cm−1) besides ν3 quanta. On the short wavelength side of ν3, the analogous transitions involve the ν2+ν6 mode (991 cm−1). The wings, and thus the spectral shape of Pd, in the ν3 region are also governed by them. They depend more strongly on temperature than stepwise transitions, because the intermediate near‐resonances favor the high rotational states.