1. Intensity distributions in <f>R</f> and <f>P</f> branches of (0–0) band of the <f>A1Π→X1Σ+</f> electronic transition of the BH molecule and determination of gas temperature in non-equilibrium plasmas
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Osiac, M., Lavrov, B.P., and Röpcke, J.
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MOLECULAR spectroscopy , *HYDROGEN - Abstract
Relative transition probabilities of spontaneous emission in the
R andP branches of theA1Π→X1Σ+ (0–0) band of BH molecule have been obtained for the first time. It was observed that measured ratios of the line strengths are in agreement with corresponding ratios of Ho¨nl–London factors. Thus, the non-adiabatic effect of perturbations is negligibly small and Ho¨nl–London formulas may be used for derivation of rovibronic population densities from measured line intensities of the (0–0)R branch of BH. The (0–0)P branch is less prospective because too much overlapping by other BH emissions cannot be avoided with the moderate resolution spectrometers usually used in plasma spectroscopy. General considerations are illustrated on the example of a low-pressure plasma of a planar microwave discharge in aH2 –Ar–B2H6 (64:33:3) gas mixture (total pressure 1–2.5 mbar , power 1.2–2.4 kW ). The values of the rotational temperatures obtained directly for the excited electronic-vibrational statesd3Πu−, v′=2 (Td2rot(H2)) andA1Π+, v′=0 (TA0rot(BH)) and those calculated in the framework of excitation-deactivation models for the groundX1Σu+, v=0 vibronic states(TX0rot(H2) andTX0rot(BH) ) have been analysed. It has been observed thatTX0rot(H2) andTX0rot(BH) are in excellent agreement, while compared to these valuesTA0rot(BH) is noticeably higher andTd2rot(H2) is about two times lower. Thus, the simultaneous measurements of intensity distributions in the rotational structure of BH andH2 emission bands can be used as a prospective method for determination of gas temperature in non-equilibrium boron and hydrogen containing plasmas. [Copyright &y& Elsevier]- Published
- 2002
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