Near-infrared diode laser spectroscopy of the HCSi radical

Abstract

The A ̃ 2 Σ +(0 1 0)– X ̃ 2 Π(0 0 0) , A ̃ 2 Σ +(0 1 0)– X ̃ 2 Π(0 1 0) , and A ̃ 2 Σ +(0 2 0)– X ̃ 2 Π(0 1 0) band spectra of HCSi radical were investigated by means of near-infrared diode laser spectroscopy to determine precise molecular constants for the X ̃ 2 Π(0 1 0) and A ̃ 2 Σ +(0 1 0) states. The detailed analysis of the rotationally resolved A ̃ 2 Σ +(0 1 0)– X ̃ 2 Π(0 1 0) band spectra, studied for the first time in the present investigation, leads to the precise determination of molecular constants for the X ̃ 2 Π(0 1 0) state associated with the Renner–Teller interaction. We obtained −0.15126663(53) and 495.00698(30) cm −1 as the Renner–Teller parameter ε and the bending vibrational frequency ω 2, respectively. Based on the molecular constants for the X ̃ 2 Π(0 0 0) and X ̃ 2 Π(0 1 0) states, the rotational levels of the A ̃ 2 Σ +(0 1 0) state were analyzed to obtain molecular constants and information on upper state perturbations. Using the available spectroscopic data, valence force fields for both the X ̃ 2 Π and A ̃ 2 Σ + states were estimated to aid in understanding the vibrational energy levels of the HCSi radical.