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Abstract:
Aluminum monofluoride (AlF) is a suitable molecule for laser cooling and trapping. Such experiments require an extensive spectroscopic characterization of the electronic structure. Two of the theoretically predicted higher lying triplet states of AlF, the counterparts of the well-characterized D1Δ and E1Π states, had experimentally not been identified yet. We here report on the characterization of the d3Π (v=0−6) and e3Δ (v=0−2) states, confirming the predicted energetic ordering of these states (J. Chem. Phys. 88 (1988) 5715-5725), as well as of the f3Σ+ (v=0−2) state. The transition intensity of the d3Π,v=3 − a3Π,v=3 band is negligibly small. This band gets its weak, unexpected rotational structure via intensity borrowing from the nearby e3Δ,v=2 − a3Π,v=3 band, made possible via spin-orbit and spin-rotation interaction between the d3Π and e3Δ states. This interaction affects the equilibrium rotational constants in both states; their deperturbed values yield equilibrium internuclear distances that are consistent with the observations. We determine the ionization potential of AlF to be 78492(1) cm-1 by ionization from the d3Π state.
