Electron-beam diagnostics of hydrogen fluoride. Optical model and its limitations

Abstract

In the study of many molecular systems by means of electron-beam diagnostics (EBD) using the Muntz method [1], one observes differences from the optical model that show up at densities above 1.10 t5 particles/cm 3. It was found that these deviations may be due to the presence of secondary processes, nonlinear in pressure, in the excitation and deactivation of the molecules: multiquantum transitions [2], excitation by secondary electrons [3], fluorescence (possibly, selective) quenching during oscillations of excited ions with molecules of the background [4], etc. Therefore, use of the EBD method in the study of new molecular systems is impossible without the development of an adequate excitation-radiation model with a detailed analysis of the probable channels of population and emptying of the radiating states. Such a model becomes more complicated, the more complex the structure of the electronic states. An EBD method has now been developed, and models for the N 2, CO 2, CO, and HC1 molecules have been constructed [5][6][7][8].This paper presents the results of a study of the emission spectra of hydrogen fluoride excited by an electron beam, results obtained from constructing a model of the excitation-deactivation processes of HF + ion, and results of determination of the scope of applicability of the EBD technique to hydrogen fluoride mixtures. The spectra of HF are of major interest in connection with the extensive use of hydrogen halides as optical media for high-power chemical lasers.1. Let us examine the process of electron-impact excitation-radiation of HF. The radiation intensity of a rotational line is [9]

Electron-beam diagnostics of rarefied gases: Activation by short electron packets

“…We consider these processes for the case of a pulsed electron beam. A detailed analysis of the working mechanisms of population and emptying of the radiating states during excitation of nitrogen molecules by a stationary electron beam is presented in [4,7].…”

“…The contribution of slow secondary, electrons to the excitation of the ions increases with increase in both the gas density and the duration of the current pulse. Since the processes of excitation of ions by fast primary and slow secondary electrons are separated in time, when measuring the light-signal intensity, it is possible to determine the contribution of secondary electrons to the excitation.Electron-beam diagnostics has been widely used in experimental studies of the gas dynamics of supersonic jets [1][2][3] and relaxation processes in various gas objects [4][5][6][7]. If the levels in the radiating state of an ion are populated only by fast primary electrons of the beam with the observance of the optical selection rules and emptying occurs by spontaneous radiation, there is a linear relationship between the spectral line intensities and the populations of the molecular levels in the ground state [8].…”