The cao d, d 1, 3δ-a3π system: Sub-doppler spectrum, rotational analysis, and deperturbation
Abstract
The CaO "Orange Arc Bands" are shown to contain transitions from both D1Δ and d3Δi upper states into both a3Πi and A’1Π lower states, as well as other not yet identified electronic band systems. More than 2000 lines in the 605-613 nm region are resolved by sub-Doppler Intermodulation Spectroscopy. Of these lines, more than 900 are definitively assigned (vibration, rotation, Ω, absolute parity) to the 0-0 and 1-1 bands of the D, d1, 3Δ-a3Π system. This is the first full rotational analysis of an alkaline earth monoxide triplet-triplet system. Assignments are based on combination differences from the sub-Doppler excitation spectra, supplemented by information from resolved laser induced fluorescence spectra. The analysis is guided by model Hamiltonians for the strong d3Δ ∼ D1Δ perturbation and for Λ-doubling in a3Π. The D1Δ state lies below d3Δ; the first known reversal of the usual ordering of 1, 3Δ states derived from a π3π’ configuration. Spin-orbit interaction between 3Δ2 and 1Δ causes the ordering of the d3Δi spin components to be irregular, with Ω = 2 highest and Ω = 3 lowest. The two 1, 3Δ Ω = 2 components are nearly 50-50 mixtures of singlet and triplet character; this mixing may represent an important pathway for spin-interconversion in CaO. © 1982 IOP Publishing Ltd.