Ab Initio Potential Energy Surface and Vibration–Rotation Energy Levels of Aluminum Monohydroxide

[Image: see text] The potential energy surface and vibration–rotation energy levels of aluminum monohydroxide in the X̃(1)A′ electronic state have been determined from ab initio calculations. The equilibrium configuration of the AlOH molecule was found to be bent, although with a wide AlOH angle of 163° and a small barrier to linearity of just 4 cm(–1). The AlOH molecule was definitely confirmed to be quasilinear. The predicted spectroscopic constants of the AlOH, AlOD, (26)AlOH, and Al(18)OH isotopologues can be useful in a future analysis of high-resolution vibration–rotation spectra of these species.