Уровневая полуэмпирическая столкновительно-излучательная модель водородной низкотемпературной плазмы электронно-циклотронного резонанса использована для анализа применимости спектральных методов диагностики по излучению триплетных состояний молекулярного водорода ( N 3 = 3 a g, 3 c u, 3 d u, 3 e u, 3 f u, 3 g g, 3 h g, 3 i g, 3 k u и 3 r g ). Показано, что вторичные процессы дают наибольший вклад в кинетику рождения и гибели триплетных состояний 3 a g, 3 c u, 3 d u, 3 e u, 3 g g, 3 h g, 3 i g и 3 r g. Наименьший вклад вторичные процессы дают в возбуждение и дезактивацию триплетных состояний 3 f u и 3 k u. Для обработки интенсивностей дипольных разрешенных переходов f 3u a3g, g3g и 3 3 k u a g может применяться упрощенная корональная модель.
The excitation kinetics of hydrogen triplet states in ECR discharge is investigated in the framework of the level-to-level zero-dimensional semiempirical collisional-radiative model of hydrogen lowtemperature plasma. Analysis of applicability of molecular emission spectroscopy for diagnostics of ECR discharge in hydrogen is performed on the basis of obtained results.
The known from literature measured two-temperature electron energy distribution function (EEDF) with groups of “cold” ( c e T, c e N ) and “hot” ( h e T, h e N ) electrons was used in the calculations. Input parameters in the model were the gas temperature Tg = 400–600 K, pressure p = (0.25–0.96)×10-2 Torr, concentrations c e N = (0.13–2.3)×1010 cm-3, h e N = (0.3–0.8)×1010 cm-3 and temperatures c e T = = 0.6–2.0 eV, h e T = 2.0–6.0 eV of electrons, the percentage of atomic hydrogen PH = 4.0 %.
The electronic relaxation time e R of the populations of the triplet states N3 of the hydrogen molecules does not exceed a few tenths of a second. The values of the steady-state concentrations of excited molecules 3 H2 N are in the range from 1.7×104 to 8.2×107 cm-3.
The stationary distribution of triplet states N3 populations and the vibrational distribution function of hydrogen molecules in the ground state differ from the Boltzmann distributions. The calculated value of the temperature of the first vibrational level 1 V g T X lies in the range from 1700 K To 3000 K. Under optimum conditions for formation of the vibrationally – excited molecules 1 2, g H X v, the processes including the excited molecules 1 2, 1 4 g H X v can give a contribution to the kinetics of excitation of triplet states 3 u c , 3 u d , 3 u e , 3 g h , 3 g i and 3 g r .
Mechanisms of the excitation and deactivation differ for different triplet state of the hydrogen molecule and are determined by the volumetric collisional-radiative processes. The composition and number of secondary processes and their hierarchy change depending on the residence time of the gas in the discharge zone.
The secondary processes give the largest contribution to the excitation and deactivation of the triplet states 3 g a , 3 u c , 3 u d , 3 u e , 3 g g , 3 g h , 3 g i and 3 g r . Secondary processes give the smallest contribution to the excitation and deactivation of the triplet states 3 u f and 3 u k . Thus the dipole transitions 3 3, 3 u g g f a g and 3 3 u g k a can be used for the spectral diagnostics of hydrogen ECR discharge on the base of a simplified coronal approximation model.
It was shown that the radiation of the system Fulcher 3 3 2 u g H d a commonly used in the spectral diagnostics does not described by a simplified coronal model in conditions of ECR discharge. This conclusion differs from that previously obtained for microwave discharge and DC discharge [65, 66]. This is due to the fact that the EEDF in ECR discharge is enriched with fast electrons compared with the distribution in these discharges. This difference leads to a greater rate of excitation of triplet states, to increase their concentrations and, consequently, to increased role of secondary processes in their excitation.
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