Characterisation of the b<sup>3</sup>Σ<sup>+</sup> state and its interaction with the A<sup>1</sup>Π state in aluminium monofluoride
Maximilian Doppelbauer, N. Walter, Simon Hofsäss, Silvio Marx, H. Christian Schewe, Sebastian Kray, Jesús Pérez‐Ríos, Boris G. Sartakov, Stefan Truppe, Gerard Meijer
Abstract
Recently, we determined the detailed energy level structure of the X<sup>1</sup>Σ<sup>+</sup>, A<sup>1</sup>Π and a<sup>3</sup>Π 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 b<sup>3</sup>Σ<sup>+</sup>,v=0 state of the AlF molecule. A rotationally resolved (1 + 2)-REMPI spectrum of the b<sup>3</sup>Σ<sup>+</sup>,v′=0 ← a<sup>3</sup>Π, v′′=0 band is presented and the lifetime of the b<sup>3</sup>Σ<sup>+</sup>,v=0 state is measured to be 190(2) ns. Hyperfine-resolved, laser-induced fluorescence spectra of the b<sup>3</sup>Σ<sup>+</sup>,v′=0 ← X<sup>1</sup>Σ<sup>+</sup>, v′′ = 1 and the b<sup>3</sup>Σ<sup>+</sup>,v ′ = 0 ← a<sup>3</sup>Π, v′′ = 0 bands are recorded to determine fine- and hyperfine structure parameters. The interaction between the b<sup>3</sup>Σ<sup>+</sup>,v = 0 and the nearby A<sup>1</sup>Π 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<sup>-1</sup>. The triplet character of the A state causes an A → a loss from the main A−X laser cooling cycle below the 10<sup>-6</sup> level.