Simulation of the SiH (A2Δ → X2Π) emission spectrum in a silane glow discharge and derivation of an improved set of molecular constants

An improved simulation of the rotational intensity distribution of the O-O emission band of the A(2) Delta-X-2 Pi transition of SiH that is experimentally obtained by optical emission spectroscopy from a silane rf glow-discharge, is reported. The improvements consist in the use of a new term value formula, a recent set of molecular constants and an extended lease squares fitting analysis for the micro-optimization of the set of constants. Thus, the rotational temperature of SiH is determined by utilizing a sufficient spectral resolution together with an experimentally determined instrument function of the optical system. The optimum fit of the emission spectrum is obtained for a rotational temperature T-ROT = 2840 +/- 50 K which is significantly higher compared to those previously reported. Furthermore, an abnormal behaviour of the observed splittings compared to the theoretical calculations is observed, while in two cases experimental measurements of Lambda-doublets were performed.