Spectroscopic investigation of the Ã [sup 1]A[sup ʺ]-X̃ [sup 1]A[sup ʹ] electronic transition of HSiNCO

The first spectroscopic observation of the previously unknown species HSiNCO has been reported. HSiNCO was generated by the fragmentation of trimethylsilylisocyanate with a high-voltage discharge source. The 0[sup 0, sub 0] band of the Ã [sup 1]A[sup ʺ]-X̃ [sup 1]A[sup ʹ] transition has been recorded with full rotational resolution using laser-induced fluorescence spectroscopy and ground and excited state rotational and centrifugal distortion constants determined. Ten additional vibrational bands belonging to HSiNCO have also been observed in the laser-induced fluorescence spectrum and have been assigned based on predicted anharmonic vibrational frequencies. Due to the large change in geometry upon excitation, a number of axis-rotation peaks have been observed in the 0 [sup 0, sub 0] band and the axis-rotation angle (θ [sub T]) has been estimated to be 0.6°±0.2°. Dispersed fluorescence spectroscopy has been carried out and ν[sub 8] (the N–C–O out-of-plane bending mode) and a number of overtones of ν[sub 4] (the Si–H wagging mode) have been observed in the ground electronic state.