The Formation of an Intense Secondary Pulsed Molecular Beam and Obtaining Accelerated Molecules and Radicals in It

摘要

A method for obtaining an intense secondary pulsed molecular beam is described. The kinetic energy of molecules in the beam can be controlled by vibrational excitation of the molecules in the source under high-power IR laser radiation. A compression shock (shock wave) is used as a source of secondary beams. The shock wave is formed in interaction between an intense pulsed supersonic molecular beam (or flow) and a solid surface. The characteristics of the secondary beam were studied. Its intensity and the degree of gas cooling in it were comparable with the corresponding characteristics of the unperturbed primary beam. Vibrational excitation of molecules in the shock wave and subsequent vibrational-translational relaxation, which occurs when a gas is expanded in a vacuum, allow the kinetic energy of molecules in the secondary beam to be substantially increased. Intense [≥ 10~(20) molecules/(sr s)] beams of SF_6 and CF_3I molecules with kinetic energies approximately equal to 1.5 and 1.2 eV, respectively, were generated in the absence of carrier gases, and SF_6 molecular beams with kinetic energies approximately equal to 2.5 and 2.7 eV with He (SF_6/He = 1/10) and H_2 (SF_6/H_2 = 1/10) as carrier gases, respectively, were obtained. The spectral and energy characteristics of acceleration of SF_6 molecules in the secondary beams were studied. The optimal conditions were found for obtaining high-energy molecules. The possibility of accelerating radicals in secondary molecular beams was demonstrated.