The A 1Σ+ → X 1Σ+ bands of the isotopic lithium hydrides

In order to obtain a better understanding of the X¹Σ⁺ ground state and the A¹Σ⁺ state potential energy curves of lithium hydride and to examine in detail the concept of “mass-reduced quantum numbers” for both an ordinary (X¹Σ⁺) and an anomalous (A¹Σ⁺) electronic state, the emission spectra of the A¹Σ⁺ → X¹Σ⁺ bands of the isotopic lithium hydrides and deuterides were photographed in the 3000–5000-Å region with a 3.4-m Ebert Spectrograph. The bands found involved v″ = 0 to 7 to various v′ = 0 to 17 for ⁶LiH, and v″ = 0 to 7 to various v′ = 1 to 16 for ⁶LiD. Additional bands involving v″ = 4 and 5 were also found for ⁷LiH. The vibrational-rotational spectroscopic analysis of ⁷LiH, ⁶LiH, and ⁶LiD are reported here, as are the reanalyses of the ⁷LiH and ⁷LiD data reported by Crawford and Jorgensen. New Rydberg-Klein-Rees (RKR) A¹Σ⁺ and X¹Σ⁺ potential curves have been constructed for each individual molecule and are reported, but detailed isotopic comparisons will be reported in subsequent publications.