Stark field induced perturbations in the ν1 + 3ν3 vibrational overtone band of acetylene

The rotationally resolved, Stark split spectrum of the ν1 + 3ν3 band of acetylene has been investigated with a high resolution molecular beam laser spectrometer. The results indicate a field induced coupling of the vb1030000〉 upper state with the vb0040000〉 state. The number of observed transitions was sufficient to allow a detailed analysis of the field induced coupling. The J-dependent polarisability and anisotropy of the polarisability of the vb1030000〉 state were measured as well as the anisotropy of the polorisability of the ground state (1.071 Å3). The coupling strength to the vb0040000〉 state, and the origin of the 4νm3 band were determined to be 0.0696 D and 12671.50 cm−1. The latter has been compared with predictors made by local mode theory.