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arXiv · 2112.09498

Spectroscopic characterization of the a$^3\Pi$ state of aluminum monofluoride

Nicole Walter·Maximilian Doppelbauer·Silvio Marx·Johannes Seifert·Xiangyue Liu·Jesús Pérez Ríos·Boris Sartakov·Stefan Truppe·Gerard Meijer
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Abstract

Spectroscopic studies of aluminum monofluoride (AlF) have revealed its highly favorable properties for direct laser cooling. All $Q$ lines of the strong A$^1\Pi$ $\leftarrow$ X$^1\Sigma^+$ transition around 227~nm are rotationally closed and thereby suitable for the main cooling cycle. The same holds for the narrow, spin-forbidden a$^3\Pi$ $\leftarrow$ X$^1\Sigma^+$ transition around 367 nm which has a recoil limit in the micro Kelvin range. We here report on the spectroscopic characterization of the lowest rotational levels in the a$^3\Pi$ state of AlF for $v=0-8$ using a jet-cooled, pulsed molecular beam. An accidental AC Stark shift is observed on the a$^3\Pi_0, v=4$ $\leftarrow$ X$^1\Sigma^+, v=4$ band. By using time-delayed ionization for state-selective detection of the molecules in the metastable a$^3\Pi$ state at different points along the molecular beam, the radiative lifetime of the a$^3\Pi_1, v=0, J=1$ level is experimentally determined as $\tau=1.89 \pm 0.15$~ms. A laser/radio-frequency multiple resonance ionization scheme is employed to determine the hyperfine splittings in the a$^3\Pi_1, v=5$ level. The experimentally derived hyperfine parameters are compared to the outcome of quantum chemistry calculations. A spectral line with a width of 1.27 kHz is recorded between hyperfine levels in the a$^3\Pi, v=0$ state. These measurements benchmark the electronic potential of the a$^3\Pi$ state and yield accurate values for the photon scattering rate and for the elements of the Franck-Condon matrix of the a$^3\Pi$ $-$ X$^1\Sigma^+$ system.

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Nicole Walter, Maximilian Doppelbauer, Silvio Marx, Johannes Seifert, Xiangyue Liu, Jesús Pérez Ríos, Boris Sartakov, Stefan Truppe, Gerard Meijer. 2021-12-17. Spectroscopic characterization of the a$^3\Pi$ state of aluminum monofluoride. https://doi.org/10.1063/5.0082601

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