Loading time is one of the most important dynamic characteristics of a magneto—optical trap. In this paper, we primarily report on a detailed experimental study of the effects of some magneto—optical trap control parameters on loading time, including the background vacuum pressure, the magnetic field gradient, and the intensities of trapping and repumping lasers. We compare the results with previous theoretical and experimental results, and give qualitative analysis. These experimental investigations offer some useful guidelines to control the loading time of magneto—optical traps. The controllable loading time achieved is helpful to enhance the signal-to-noise ratio of photoassociation spectroscopy, which is remarkably improved from 7 to 28.6.
We have performed photoassociative spectroscopy of ultracold potassium atoms in a high-density vapor-cell magneto-optical trap (MOT) in which atoms are confined predominantly in "dark" hyperfine levels that do not interact with the trapping light. Three well-resolved vibrational series (one strong and two weak) of the
39K2 molecule are observed within 8 ${\mathrm{cm}}^{\ensuremath{-}1}$ below the
42P23 atomic limit. One of the series is identified as the ${0}_{g}^{\ensuremath{-}}$ pure long-range state and the other two are assigned to the
0u+ and
1g states. These photoassociative spectra are obtained by measuring reductions in the trap fluorescence due to trap loss induced by an intense photoassociation laser. By using a vapor-cell-dark MOT technique, we achieve atomic densities greater than
1011 ${\mathrm{cm}}^{\ensuremath{-}3}$, increasing our trap loss signals by an order of magnitude compared to a normal MOT.
We use time-of-flight mass spectroscopy to detect the ultracold ground state Cs2 molecules formed directly by a photoassociation due to the trapping laser beams and repumping laser beam in a magneto-optical trap. We investigate the dependences of the Cs2+ intensity on operating voltage of micro-channel-plate, accelerating field intensity and duration time of the accelerating field. The experimental results are consistent with theoretical fitting. We obtain the best optimal parameters suited to our experimental condition, which is important for the future experiment on ultracold molecule photoassociation and photoionization spectroscopy.