Electronic Population Inversions by Fluid-Mechanical Techniques

Abstract

The promotion of population inversions between electronic excited states by fluid-mechanical techniques is suggested. Three methods are proposed as illustrations, and the possible degree of inversion in each is estimated. The first makes use in part of the known inversion obtained in excited Ne levels by energy transfer from He metastables. A flow system separates the region of excitation of the He from the region of the resonant excitation of the Ne by the He metastable, and the undesirable electron excitation of the lower Ne state is avoided. The second proposal involves the supersonic expansion of a dissociated mixture of O and H atoms obtained by combustion. An inversion is anticipated between the v′ = 2 and v′ = 1 vibrational levels of the OH(2Σ+) state through the process of inverse predissociation occurring during the expansion. The third illustration involves the rapid expansion of a highly excited gas where radiative depopulation of the lower state promotes an inversion. Results of exploratory experiments involving this particular scheme are discussed. However, it was not possible to observe a population inversion within the noise level of the experiment which involved the sudden expansion of Xe heated by a shock tube.

Flame-Sheet Analysis of C. W. Diffusion-Type Chemical Lasers, I. Uncoupled Radiation

“…Vibrational relaxation of HF(v) by V-V collisions and by V-T collisions is defined in Table 1 by Eqs. (4)(5)(6)(7)(8)(9) and by Eqs. (10)(11)(12)(13)(14)(15), respectively.…”

“…3 ' 4 The technique of using a nonequilibrium, high-speed convective flow to produce continuous laser action for a premixed molecular laser system was first proposed in Ref. 5 (see also Ref. 6).…”

Optical history of the high-energy gas dynamic laser

“…4.1 General Two curvature parameters characterize a particular resonator configuration: gi = 1 -L/R1 and g2 = 1 -L/R2 where L is the length of the resonator and Ri and R2 are the radii of curvature of the two resonator mirrors. Stable and later, unstable resonator concepts, together with IMOPA concepts, provided a path to high quality, high efficiency power extraction which exploited the GDL's potential.…”

Chemical Laser Action in Low Pressure Metal Vapor Flames

“…the excited state population higher than the lower state population) must be obtained if the stimulated emission process is to result in amplification. A point of interest is that while all existing gas dynamic lasers utilize vibrational-rotational population inversion, early proposals of Hurle and Hertzberg (1965) Also excluded from consideration as chemical lasers are systems where chemically powered light sources (e.g. flames, shock-excited gases) are used to optically pump a laser system, (Conger, Johnson, et al, 1966, Stokes, 1970, Wieder, 1970 and systems where molecular systems are pumped by optical, (Hajdu, 1963, Gorog, 1961, Askarian, Gol'ts and Rabinovich, 1966, Ewing, Milstein and Berry, 1970, Bennett, 1965 gas dynamic shock or electrical discharge methods: A particular case of non-chemical excitation is the metal vapor laser in which electronically excited atoms are produced by electrical discharge or optical pumping, (Bennett, 1965, Mishakov, Tibolov, and Shukhtin, 1971, Sorokin and Lankard, 1971) but in which chemical reactions play no part at all.…”