Experimental and theoretical investigation of the rotational structure of the Al–H2/D2 complex

Abstract

The rotational structure of the Al–H2/D2 complex is investigated in a collaborative experimental and theoretical study. The isotopomeric complexes were prepared in a pulsed supersonic beam, and their 3d←3p and 4p←3d electronic transitions recorded through laser fluorescence excitation spectroscopy. Transitions to quasibound excited vibronic levels were observed by monitoring emission from lower excited Al atomic levels, formed by nonradiative decay of the excited complex. In some bands, the Lorentzian width was sufficiently narrow that resolved rotational lines were observed. Rotational analysis of several bands which typify the two different patterns of observed rotational structure is presented. The derived rotational constants and parity splitting parameters for the ground Al(3p)–oH2/pD2 bend-stretch levels were compared with constants computed from fits to J- and parity-dependent energies calculated with new Al(3p)–H2 potential energy surfaces (PESs), which extend those recently reported by Williams and Alexander [J. Chem. Phys. 112, 5722 (2000)] by inclusion of the dependence on the H2 bond distance. The experimental and computed rotational constants were found to be in very good agreement. This provides strong support for the reliability of the calculated PESs.