Pendular state spectroscopy of an asymmetric top: Parallel and perpendicular bands of acetylene-HF

We report here a comprehensive theoretical and experimental study of the pe ndular state spectroscopy of a near-prolate asymmetric top molecule and con sider the specific case of the acetylene-HF binary complex in a static elec tric field. The experiments were carried out using the optothermal detectio n method and the spectra were recorded in an electric field of sufficient m agnitude to give rise to substantial orientation in a number of states. The calculated and experimental spectra are compared for different vibrational band types and polarization configurations. In this way we have identified the states that give the best orientation and thus are well suited to phot odissociation studies. The hybridized orientational probability distributio ns are presented for the relevant states. (C) 1999 American Institute of Ph ysics. [S0021-9606(99)02501-5].