Near-infrared diode laser spectroscopy of the HCSi radical

The (A) over tilde (2)Sigma(+)(010)-(Chi) over tilde (2)Pi(000), (A) over tilde (2)Sigma(+)(010)-(Chi) over tilde (2)Pi(010), and (A) over tilde (2)Sigma(+)(020)-(Chi) over tilde (2)Pi(010) band spectra of HCSi radical were investigated by means of near-infrared diode laser spectroscopy to determine precise molecular constants for the (Chi) over tilde (2)Pi(010) and (A) over tilde (2)Sigma(+)(010) states. The detailed analysis of the rotationally resolved (A) over tilde (2)Sigma(+)(010)(Chi) over tilde (2)Pi(010) band spectra, studied for the first time in the present investigation, leads to the precise determination of molecular constants for the (Chi) over tilde (2)Pi(010) state associated with the Renner-Teller interaction. We obtained -0.15126663(53) and 495.00698(30)cm(-1) as the Renner-Teller parameter epsilon and the bending vibrational frequency omega(2), respectively. Based on the molecular constants for the (Chi) over tilde (2)Pi(000) and (Chi) over tilde (2)Pi(010) states, the rotational levels of the (A) over tilde (2)Sigma(+)(010) state were analyzed to obtain molecular constants and information on upper state perturbations. Using the available spectroscopic data, valence force fields for both the (Chi) over tilde (2)Pi and (A) over tilde (2)Sigma(+) states were estimated to aid in understanding the vibrational energy levels of the HCSi radical. (C) 2003 Elsevier Inc. All rights reserved.