Actinometry of O, N and F atomsстатья

Статья опубликована в высокорейтинговом журнале

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Дата последнего поиска статьи во внешних источниках: 8 августа 2017 г.

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[1] Actinometry of o, n and f atoms / D. V. Lopaev, A. V. Volynets, S. M. Zyryanov et al. // Journal of Physics D - Applied Physics. — 2017. — Vol. 50, no. 7. — P. 075202. The applicability of actinometry for measuring the absolute concentration of O, N and F atoms in discharge plasma was studied. For this purpose, concentrations of these atoms were measured downstream of an ICP plasma by means of the actinometry method and of appearance potential mass-spectrometry (APMS). Comparison of the results showed good agreement between the two methods. Since the excitation cross sections of electron states O(3p 3P) and O(3p 5P) applied in actinometry are well tested, this allows using the APMS method for absolute calibration of the theoretical excitation cross sections for N and F atoms. As a result, total excitation cross sections sigma(total)of the atomic levels N(3p 4Po), F(3p 2Po)and F(3p 4Do) have been obtained for the first time. Since different types of electron energy distribution function (EEDF) were observed (Maxwellian, bi-Maxwellian and Druyvesteyn)the influence of these possible EEDF types on actinometric coefficients CX,Ar (X = O, N, F), that link the ratio of the atom and actinometer intensities IX/IAr with that of their concentrations [X]/[Ar], was also analyzed. It was shown that at the same ionization rate (effective electron temperature) the excitation rate constants kX,Ar are highly sensitive to the shape of EEDF,whereas actinometric coefficients CX,Ar depend on it only slightly. Dependence of actinometric coefficients on electron temperature CX,Ar(Te)is positive if the emitting level of the X-atom is lower than that of the actinometer, and negative if vice versa. The energy difference between the emitting states of O and Ar atoms is maximal (∼3 eV), so that CO,Ar(Te)is not constant for a whole range of electron temperatures typical for discharge plasmas (∼2–8 eV). For nitrogen atoms CN,Ar(Te)varies considerably with Te only when Te < 4 eV. In the case of fluorine atoms the energy difference of emitting F and Ar states is only ∼1 eV and coefficient CF,Ar(Te)is nearly constant in a wide region of Te > 1.5 eV. [ DOI ]

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