The rotationally resolved A 1A″←X 1A′ spectrum of expansion cooled NCNO: Vibrational fundamentals, rotational constants, and perturbations

The laser excitation spectrum (à 1A″←X̃ 1A′, T′0 =11 339 cm−1) of expansion cooled nitrosyl cyanide (NCNO) has been observed at rotational resolution using the technique of two-photon photodissociation followed by laser induced fluorescence detection of the CN fragment. All six excited state fundamental vibrations are assigned. The à 1A″ state geometry is derived from the measured rotational structure, and corresponds to a planar, trans conformation. Most of the bands are strongly perturbed by ground state levels, and there is strong evidence suggesting that à 1A″/X̃ 1A′ mixing leads to the vibrational predissociation.