Rovibrational Spectra of LiH₂⁺, LiHD⁺ and LiD₂⁺ Determined from FCI Property Surfaces

Full configuration interaction (FCI) has been used in conjunction with the lithium [6s5p3d1f] (Iron, M. A.; et al. Mol. Phys. 2004, 101, 1345) and hydrogen aug-cc-pVTZ basis sets to construct an 83-point potential energy surface of the 1A1 ground state of 7LiH2+. Vibrational and rovibrational wave functions of the6,7LiH2+, 6,7LiHD+, and 6,7LiD2+ ground states were calculated variationally using an Eckart−Watson Hamiltonian. For 7LiD2+, rovibrational transition frequencies for K = 0, 1, 2 and J ≤ 10 are within ca. 0.1% of recent experimental values (Thompson, C. D.; et al. J. Chem. Phys. 2006, 125, 044310). A 47-point FCI dipole moment surface was embedded in the rovibrational Hamiltonian to calculate vibrational and rovibrational radiative properties. At 296 K, with v ≤ 4 and J ≤ 4, the 202 ← 303 rotational transition in the |001〉 band was found to have the greatest spectral intensity with respect to the ground electronic states of 6,7LiH2+, 6,7LiHD+, and 6,7LiD2+. In each case, the most intense rovibrational transitions have been assigned unequivocally using the J, Ka, Kc assignment scheme.