Laser excitation spectroscopy of the (A)over-tilde(3)Pi(u)-(X)over-tilde(3)Sigma(-)(g) transition of the NCN radical .2. The nu(2) hot band

The (010)-(010) band of the (A) over tilde(3) Pi(u) - (X) over tilde(3) Sigma(g)(-) transition of the NCN radical at 328 nm has been reexamined at Doppler-limited resolution by laser excitation spectroscopy. The molecule was generated in a microwave discharge through N-2 and CF4 in helium. Both the (3) Delta(g)-(3) Pi(u) and the (3) Sigma(g)(+/-)-3 Pi(u), vibronic components of the transition have been observed and rotationally analyzed. The Renner-Teller parameter, epsilon omega(2), for NCN in the excited (A) over tilde(3) Pi(u) state is determined to be -91.1213(16) cm(-1). Estimates for the ground and excited state bending vibrational wavenumbers of 437.7(14) and 533.95(70) cm(-1) respectively have been obtained. (C) 1997 Academic Press.