TY - JOUR

T1 - Intensity distributions in R and P branches of (0-0) band of the A1Π → X1Σ+ electronic transition of the BH molecule and determination of gas temperature in non-equilibrium plasmas

AU - Osiac, M.

AU - Lavrov, B. P.

AU - Röpcke, J.

PY - 2002/8/15

Y1 - 2002/8/15

N2 - Relative transition probabilities of spontaneous emission in the R and P branches of the A1Π → 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 Hönl-London factors. Thus, the non-adiabatic effect of perturbations is negligibly small and Hönl-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 a H2-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 states d3Πu -, ν′ = 2 (Td2 rot(H2)) and A1Π+, ν′ = 0 (TA0 rot(BH)) and those calculated in the framework of excitation-deactivation models for the ground X1Σu +, ν = 0 vibronic states (TX0 rot(H2) and TX0 rot(BH)) have been analysed. It has been observed that TX0 rot(H2) and TX0 rot(BH) are in excellent agreement, while compared to these values TA0 rot(BH) is noticeably higher and Td2 rot(H2) is about two times lower. Thus, the simultaneous measurements of intensity distributions in the rotational structure of BH and H2 emission bands can be used as a prospective method for determination of gas temperature in non-equilibrium boron and hydrogen containing plasmas.

AB - Relative transition probabilities of spontaneous emission in the R and P branches of the A1Π → 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 Hönl-London factors. Thus, the non-adiabatic effect of perturbations is negligibly small and Hönl-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 a H2-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 states d3Πu -, ν′ = 2 (Td2 rot(H2)) and A1Π+, ν′ = 0 (TA0 rot(BH)) and those calculated in the framework of excitation-deactivation models for the ground X1Σu +, ν = 0 vibronic states (TX0 rot(H2) and TX0 rot(BH)) have been analysed. It has been observed that TX0 rot(H2) and TX0 rot(BH) are in excellent agreement, while compared to these values TA0 rot(BH) is noticeably higher and Td2 rot(H2) is about two times lower. Thus, the simultaneous measurements of intensity distributions in the rotational structure of BH and H2 emission bands can be used as a prospective method for determination of gas temperature in non-equilibrium boron and hydrogen containing plasmas.

KW - Boron

KW - Gas temperature

KW - Hydrogen

KW - Molecular spectroscopy

KW - Plasma diagnostics

UR - http://www.scopus.com/inward/record.url?scp=0037102696&partnerID=8YFLogxK

U2 - 10.1016/S0022-4073(01)00268-0

DO - 10.1016/S0022-4073(01)00268-0

M3 - Article

AN - SCOPUS:0037102696

VL - 74

SP - 471

EP - 491

JO - Journal of Quantitative Spectroscopy and Radiative Transfer

JF - Journal of Quantitative Spectroscopy and Radiative Transfer

SN - 0022-4073

IS - 4

ER -