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Abstract

Recently, we determined the detailed energy level structure of the X¹Σ⁺, A¹Π and a³Π states of AlF that are relevant to laser cooling and trapping experiments [Truppe et al., Phys. Rev. A. 100 (5), 052513 (2019)]. Here, we investigate the b³Σ⁺,v=0 state of the AlF molecule. A rotationally resolved (1 + 2)-REMPI spectrum of the b³Σ⁺,v′=0 ← a³Π, v′′=0 band is presented and the lifetime of the b³Σ⁺,v=0 state is measured to be 190(2) ns. Hyperfine-resolved, laser-induced fluorescence spectra of the b³Σ⁺,v′=0 ← X¹Σ⁺, v′′ = 1 and the b³Σ⁺,v ′ = 0 ← a³Π, v′′ = 0 bands are recorded to determine fine- and hyperfine structure parameters. The interaction between the b³Σ⁺,v = 0 and the nearby A¹Π state is studied and the magnitude of the spin–orbit coupling between the two electronic states is derived using three independent methods to give a consistent value of 10(1) cm^-1. The triplet character of the A state causes an A → a loss from the main A−X laser cooling cycle below the 10^-6 level.