LASER SPECTROSCOPY OF C-3 - STIMULATED-EMISSION AND ABSORPTION-SPECTRA OF THE (A)OVER-TILDE(1)PI(U)-(X)OVER-TILDE(1)SIGMA(G)(+) TRANSITION

Several bands of the (A) over tilde (IIu)-I-1-(X) over tilde(1) Sigma( g)(+) transition of C-3 have been observed between 24868 and 25140 cm( -1) in a liquid-nitrogen cooled discharge through methane and helium. The spectra were taken cm with a frequency-doubled cw Ti:sapphire ring laser, Bands were observed either in stimulated emission or in absorp tion, The stimulated emission spectra include the bands 020-000 (IIu(- )-I-1)-(1) Sigma(g)(+), 020-020 (IIu(-)-I-1)-(1) Sigma(g)(+), 020-020 (IIu(-)-I-1)-(1) Delta(g), and 020-020 (1) Phi(u)-(1) Delta(g). Analys is shows that entanglement of the 020-000 (IIu(-)-I-1)-(1) Sigma(g)(+) band with tile previously unanalyzed 020-020 (1) Phi(u)-(1) Delta(g) band has led to flaws in past rotational analyses of the (A) over tild e 020 (IIu(-)-I-1) level. The absorption spectra include two bands for which the positions of the Q branch heads were reported previously [C an. J. Phys. 45, 4103 (1967)]. We confirm that the first band is the 0 02-100 (IIu)-I-1-(1) Sigma(g)(+) band, as suggested by Balfour Et ad. [J. Chem. Phys. 101, 10343 (1994)], and show that the second is the 10 2-200 (IIu)-I-1-(1) Sigma(g)(+) band. (C) 1997 American Institute of P hysics.