[en] The laser frequency dependence of the enrichment factors in the separation of silicon isotopes by infrared multi-photon dissociation (MPD) were calculated. Based on the knowledge of the isotopic shifts, a simple model was developed to estimate the dependence of the MPD yield on the laser frequency. The results agree well with the experimental results reported elsewhere. This new method allows us to determine the relative contribution to the MPD yield of the 6 Si₂F₆ isotopic species and to explain the behavior of the enrichment factors. (author)

[en] Experiments were performed for observation of the vibrational predissociation of UF₆ clusters in a supersonic Laval nozzle with a pulsed Raman laser beam (16 μm). The frequency of the Raman laser beam was tuned to a ν₃ vibrational mode of UF₆ clusters. The time-dependent change in the concentration of UF₆ monomers distributed in the ground state was monitored with an infrared diode laser spectrometer in which the frequency of laser beam was fixed at the v=1 <- 0 transition (627.7 cm^-1) of ν₃ mode of ²³⁸UF₆ monomer in the Laval nozzle. Our results indicate that UF₆ monomers in the ground state increased immediately after the Raman laser pulse was applied for dissociation of UF₆ clusters and subsequently after approximately 4 μs they decreased more slowly than the increase because the recombination, previous to the clustering, of UF₆ monomers took place. (author)