An optical-optical double resonance experiment in LiH molecules: lifetime measurements in the C state.
An optical-optical double resonance sub-Doppler experiment is used to measure short nonradiative lifetimes in the C (1)Sigma(+) state of LiH. These lifetimes are expected to result from the strong electronic interaction between the C (1)Sigma(+) state and the continuum of the A (1)Sigma(+) state and to vary with the vibrational quantum number, from nanoseconds to milliseconds. The experimental setup combines a molecular beam of LiH, a first cw laser beam locked to a given A-X absorption line, and a second cw laser beam scanned over C-A absorption profiles. Analysis of these absorption profiles in terms of Voigt profiles shows that their Lorentzian components significantly vary with the vibrational quantum numbers of the C state. Nonradiative decay rates deduced this way are systematically larger than the calculated ones but their variations are similar. Coherent saturation effects cannot be invoked to explain this discrepancy.
Laboratoire Aimé Cotton CNRS, Bat 505, 91405 Orsay Cedex, France.
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