Selective multiphoton IR dissociation of SF6 molecules under nonequilibrium conditions of a pulsed gasodynamically cooled molecular flow interacting with a solid surface

The process of the isotope-selective multiphoton IR dissociation of SF6 mol ecules under the non-equilibrium conditions of a pulsed gasodynamically coo led molecular flow intel acting with a solid surface was experimentally stu died. The SF6 molecules dissociate as a result of excitation in a shock wav e generated in the flow, in the flow incident onto the sold surface, and in an unperturbed flow (in the absence of the solid). The experiment was base d on detecting the luminescence from HF* molecules (lambda = 2.5 mum) accom panying the SF6 dissociation in the presence of H-2 or CH4, the emission in tensity being a measure of the SF6 dissociation yield. The molecular beam p arameters were studied. The time-of-flight spectra of SF6 in the how intera cting with the surface were measured under various experimental conditions. The spectral and energy characteristics of the SF6 dissociation process we re determined in the flow interacting with the solid surface and in the unp erturbed flow. The dissociation product (SF4) yield was measured and the co efficient of its enrichment with the S-34 isotope was determined. It is dem onstrated that, using the shock wave formation, it is possible to increase the efficiency of the isotope-selective dissociation of SF6 molecules. An e xplanation of the observed results is proposed. The gas density and tempera ture in the incident how and in the shock wave were estimated. The results are analyzed and compared to the other published data on the SF6 dissociati on in a molecular beam. (C) 2001 MAIK "Nauka/Interperiodica".