Characterisation of the state and its interaction with the state in aluminium monofluoride

Abstract

Recently, we determined the detailed energy level structure of the (Formula presented.), (Formula presented.) and (Formula presented.) 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 (Formula presented.) state of the AlF molecule. A rotationally resolved (1 + 2)-REMPI spectrum of the (Formula presented.) band is presented and the lifetime of the (Formula presented.) state is measured to be 190(2) ns. Hyperfine-resolved, laser-induced fluorescence spectra of the (Formula presented.) and the (Formula presented.) bands are recorded to determine fine- and hyperfine structure parameters. The interaction between the (Formula presented.) and the nearby (Formula presented.) 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 (Formula presented.). The triplet character of the A state causes an (Formula presented.) loss from the main A−X laser cooling cycle below the 10 (Formula presented.) level.