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

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.

16 pages, 9 figures

References in corpus (4)

• Cold molecules: Progress in Quantum Engineering of Chemistry and Quantum Matter
• Ultracold molecules: new probes on the variation of fundamental constants
• The radiative lifetime of metastable CO ($a^3\Pi ,v=0$)
• Characterisation of the $b^3{\Sigma }^{+},v=0$ State and Its Interaction with the $A^1\Pi$ State in Aluminium Monofluoride