The(C)over-tilde-(X)over-tilde electronic spectrum of the SrNC free radical: a jet-cooled investigation

The quasi-continuous band system of the SrNC free radical first observed many years ago by Pasternack and Dagdigian, and attributed to the (C) over tilde-(K) over tilde electronic transition, has been subjected to a jet-cooled laser-induced fluorescence study. This new work reveals abundant vibrational structure that was largely hidden in the earlier study. The spectrum is not amenable to a simple vibrational analysis, presumably because of extensive perturbations. However, the fact that the structure spans more than 3500 cm(-1) reveals that SrNC undergoes a major geometry change on electronic excitation. Since it is known to be linear in its ground electronic state ((2)Sigma (+)), th, activity of the bending vibration in the spectrum suggests that SrNC adopts a nonlinear equilibrium geometry on excitation. (C) 2000 Elsevier Science B.V. All rights reserved.