Fourier transform emission spectrum of the HCSi radical, (A)over-tilde (2)Sigma(+)-(X)over-tilde (2)Pi(i) transition

A Fourier transform emission spectrum of the HCSi, (A) over tilde (2)Sigma( +)-(X) over tilde (2)Pi(i) transition was observed by means of a Schuler-ty pe discharge tube in the 9000-14 000 cm(-1) spectral region. Three bands wh ose origins appeared at 12 934.406, 11 766.721, and 10 752.430 cm(-1) were rotationally analyzed and assigned, respectively, to the (100)-(000), (000) -(000), and (000)-(100) bands. The new ab initio calculated A((X) over tild e (2)Pi) spin-orbit constant agrees well with the experimental value. Weak rotational perturbations in the (100) level of the upper electronic state a re likely due to highly excited vibrational levels of the ground state, whe reas the "anomalous" increase of the spin-rotation constant in the (100) le vel of the ground state relative to the (000) level was shown to result of a Fermi interaction with the (020) (2)Pi Renner-Teller components. A compar ison was made between the rotational constants of the (000) ground state le vel with those obtained in concomitant works. (C) 2000 American Institute o f Physics. [S0021-9606(00)01124-7].