Spectroscopy and isotope shifts of the4s3d1D2–4s5p1P1repumping transition in magneto-optically trapped calcium atoms

Abstract

We investigate a repumping scheme for magneto-optically trapped calcium atoms. It is based on excitation of the $4s3{d}^{1}{D}_{2}$--$4s5{p}^{1}{P}_{1}$ transition at $672$ nm with an extended cavity diode laser. The effect of the repumping is approximately a factor of three increase in trap lifetime and a doubling of the trapping efficiency from a Zeeman slowed thermal beam. Added to this, the 672-nm laser repumps atoms from an otherwise dark state to yield an overall increase in detected fluorescence signal from the magneto-optic trap (MOT) of more than an order of magnitude. Furthermore, we report isotope shift measurements of the $672$-nm transition, for the first time, for four naturally occurring even isotopes. Using available charge radii data, the observed shifts, extending up to $4.3$ GHz, display the expected linear dependence in a King plot analysis. The measured shifts are used to determine the isotope shifts of the remaining $^{41,43,46}\mathrm{Ca}$ isotopes. These might be of interest where less abundant isotopes are used enabling isotope selective repumping, resulting in enhanced trapping and detection efficiencies.