Characterisation of the $b^3\Sigma^+, v=0$ State and Its Interaction with the $A^1\Pi$ State in Aluminium Monofluoride

TL;DR

This study characterizes the $b^3\Sigma^+, v=0$ state of AlF, measures its lifetime, and investigates its interaction with the $A^1\Pi$ state, providing insights relevant for laser cooling applications.

Contribution

The paper provides the first detailed analysis of the $b^3\Sigma^+, v=0$ state, including its hyperfine structure, lifetime, and spin-orbit interaction with the $A^1\Pi$ state in AlF.

Findings

Measured the lifetime of the $b^3\\Sigma^+, v=0$ state as 190(2) ns.

Determined the spin-orbit coupling between $b^3\\Sigma^+, v=0$ and $A^1\\Pi$ states as 10(1) cm$^{-1}$.

Identified the triplet character of the $A$ state causes minimal loss in laser cooling cycle.

Abstract

Recently, we determined the detailed energy level structure of the $X^1\Sigma^+$, $A^1\Pi$ and $a^3\Pi$ states of AlF that are relevant to laser cooling and trapping experiments. Here, we investigate the $b^3\Sigma^+, v=0$ state of the AlF molecule. A rotationally-resolved (1+2)-REMPI spectrum of the $b^3\Sigma^+, v'=0 \leftarrow a^3\Pi, v''=0$ band is presented and the lifetime of the $b^3\Sigma^+, v=0$ state is measured to be 190(2)~ns. Hyperfine-resolved, laser-induced fluorescence spectra of the $b^3\Sigma^+, v'=0 \leftarrow X^1\Sigma^+, v''=1$ and the $b^3\Sigma^+, v'=0 \leftarrow a^3\Pi, v''=0$ bands are recorded to determine fine- and hyperfine structure parameters. The interaction between the $b^3\Sigma^+, v=0$ and the nearby $A^1\Pi$ 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 $A\rightarrow a$ loss from the main $A-X$ laser cooling cycle below the 10$^{-6}$ level.