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Abstract

We report on hyperfine-resolved laser spectroscopy of the A²Π ←X²Σ⁺ transition of MgF, relevant for laser cooling. We recorded 25
rotational transitions with an absolute accuracy of better than 20 MHz,
assigned 56 hyperfine lines and determined precise rotational, fine and
hyperfine structure parameters for the A²Π state. The radiative lifetime
of the A²Π state was determined to be 7.2(3) ns, in good agreement with
\textit{ab initio} calculations. The transition isotope shift between bosonic
isotopologues of the molecule is recorded and compared to predicted values
within the Born-Oppenheimer approximation. We measured the Stark effect of
selected rotational lines of the A²Π ←X²Σ⁺ transition
by applying electric fields of up to 10.6 kV cm^-1 and determined the
permanent electric dipole moments of ²⁴MgF in its ground X²Σ⁺ and
first excited A²Π states to be μ_X=2.88(20) D and μ_A=3.20(22) D,
respectively. Based on these measurements, we caution for potential losses from
the optical cycling transition, due to electric field induced parity mixing in
the excited state. In order to scatter 10⁴ photons, the electric field must
be controlled to below 1 V cm^-1.