An experimental study of the rotational distribution of N₂⁺B (v) states excited by electron beam impingement upon helium and nitrogen gas mixtures

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Virginia Polytechnic Institute and State University

A large number of atomic helium states are excited by inelastic collisions. That excitation may be induced by various methods, including gas discharges, flowing afterglows and electron beams. The first negative nitrogen bands, N₂⁺(B²Σᵤ⁺- X²Σg⁺), have been observed with relatively high intensity from small quantities of nitrogen in helium, also induced by such methods. These bands have been studied by passing 26 kev electrons through mixtures. The resolved rotational spectra of the (0,0) and (0,1) bands have been analyzed as functions of pressure and mixture. An observed enhancement of the intensities has been interpreted in terms of selectively enhanced N₂⁺B rotational state populations. The particular helium species responsible for the enhancement are discussed. Experimental results are compared with a general"phase space" approach for calculating the reaction cross sections.