Spectroscopy and dynamics of van der Waals complexes containing the aluminum atom and of several small molecules

The 4s, 3d, 4p, 4 d, 6s, 5d ← 3p electronic transitions in the Al-H₂/D₂ complex have been characterized by laser spectroscopy. In all cases, the excited states decay by predissociation. Complicated patterns of vibronic bands with various Lorentzian widths were observed. Many spectral features were assigned with help from ab initio calculations. A long progression was assigned to transition to a strongly bound charge transfer state correlating with the Al(3d) + H₂ asymptote. Some features associated with the 3d, 4p ← 3 p transitions were narrow enough to allow a rotational analysis, and the derived ground-state rotational constants and parity splitting parameters were found in very good agreement with calculated values. The 4s ← 3p transition was found to be unique in that a broad unstructured feature was observed, indicative of the repulsive nature of the excited state of the complex. Coupling to this repulsive state is believed to be responsible for the predissociation of higher-energy, bound levels of the complex. The 4s, 3d ← 3p electronic transitions in the AlNe, Al-N₂ and Al-CH₄ complexes were also investigated.; Four vibrational progressions of the gallium dimer in the spectral range 33600–36800 cm−1 were observed. Two progressions were assigned as electronic transitions to the 33Π _g and 21Π_g states from the ground X3Π_u state. A potential energy curve for the 33Π_g state was derived, and an upper limit for the ground-state dissociation energy was obtained.; A theoretical treatment for the AlH/AlD b3Σ − state decay dynamics was carried out. Both radiative and nonradiative decays were considered. The nonradiative decay dominates over the radiative decay for rotational/fine-structure levels in the v ′ = 0 vibrational band. An avoided crossing between the 1 3Σ+ and 23Σ+ states was found to have a significant influence on the lifetimes of the rotational/fine-structure levels of the b3Σ− state.; Collisional energy transfer involving the four Renner-Teller components of the (012) vibrational manifold of NCO(X˜ 2Π) with argon was studied. In several cases, transfer between specified Renner-Teller levels was observed. The derived removal rates were found to be much larger than those for relaxation of the pure bend levels.