Bending vibrational wave numbers in the (a)over-tilde 3Πu and (b)over-tilde 3Πg states of C3

The spectrum of the 050 (3)Sigma(u)(-)-010 (3)Sigma(g)(-) band of the (b) over tilde (3)Pi(g)-(a) over tilde (3)Pi(u) electronic transition of C-3 is reported. The data, when considered with the previously observed 010 (3)Sigma(u)(-)-010 (3)Sigma(g)(-) band, measure the absolute interval between the 050 (3)Sigma(u)(-) and 010 (3)Sigma(u)(-) levels of the (b) over tilde (3)Pi(g) state. This interval, and the Renner parameters for (a) over tilde (3)Pi(u) and (b) over tilde (3)Pi(g) [D. W. Tokaryk and S. Civis, J. Chem. Phys. 103, 3928 (1995)], allow us to greatly improve estimates of the bending vibrational wave numbers in these electronic states. The values (542.3 cm(-1) for (a) over tilde (3)Pi(u), and 392.4 cm(-1) for (b) over tilde (3)Pi(g)) predict the origins of all previously reported bands of (b) over tilde (3)Pi(g) -(a) over tilde (3)Pi(u) involving bending to within 13 cm(-1). (C) 2002 American Institute of Physics.