Infrared laser multiphoton excited SF6shows infrared fluorescence spectra characteristic of the laser excitation process. These fluorescence experiments were conducted under dilute conditions so that the effects of collisions are essentially eliminated. After laser preparation fluorescence from molecules populating the quasicontinuum and discrete level ensembles are observed. These ensembles show distinctly different spectral characteristics which help demark energy zones which these types of levels occupy. Discrete levels which exist at lower vibrational energies show sharp fluorescence characteristic of energy localized in the laser excited mode. Quasicontinuum levels which exist at chemically interesting energies reveal that collisionless intramolecular relaxation has occured. Model calculations on thermally prepared and infrared laser prepared SF6molecules allow the assignment of the average energy deposition into SF6as a function of fluence, and of the population distribution of SF6within the quasicontinuum. The model simulations of the fluorescence show that the population distribution of the quasicontinuum SF6ensemble is nearly Boltzmann. At the lowest energies, however, a significant excess population of SF6molecules is trapped within the discrete states.
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