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

Abstract

The process of the isotope-selective multiphoton IR dissociation of SF₆ molecules under the non-equilibrium conditions of a pulsed gasodynamically cooled molecular flow interacting with a solid surface was experimentally studied. The SF₆ molecules dissociate as a result of excitation in a shock wave 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 based on detecting the luminescence from HF^* molecules (λ ≈ 2.5) μm) accompanying the SF₆ dissociation in the presence of H₂ or CH₄, the emission intensity being a measure of the SF₆ dissociation yield. The molecular beam parameters were studied. The time-of-flight spectra of SF₆ in the flow interacting with the surface were measured under various experimental conditions. The spectral and energy characteristics of the SF₆ dissociation process were determined in the flow interacting with the solid surface and in the unperturbed flow. The dissociation product (SF₄) yield was measured and the coefficient of its enrichment with the ³⁴S isotope was determined. It is demonstrated that, using the shock wave formation, it is possible to increase the efficiency of the isotope-selective dissociation of SF₆ molecules. An explanation of the observed results is proposed. The gas density and temperature in the incident flow and in the shock wave were estimated. The results are analyzed and compared to the other published data on the SF₆ dissociation in a molecular beam.