Radiative collisional heating at the Doppler limit for laser-cooled magnesium atoms

We report Monte Carlo wave function simulation results on cold collisions between magnesium atoms in a strong red-detuned laser field. This is the normal situation, e.g., in magneto-optical traps (MOT). The Doppler limit heating rate due to radiative collisions is calculated for ${}^{24}\mathrm{Mg}$ atoms in an MOT based on the ${}^{1}S_0\text{−}{}^{1}P_1$ atomic laser cooling transition. We find that radiative heating does not seem to affect the Doppler limit in this case. We also describe a channeling mechanism due to the missing $Q$ branch in the excitation scheme, which could lead to a suppression of inelastic collisions, and find that this mechanism is not present in our simulation results due to the multistate character of the excitation process.

Figure 1

The coupling scheme for the ${}^1\Sigma _g^{+}$ ground-state partial wave $l$ and the ${}^1\Sigma _u^{+}$ excited state rotational state $J$.

Figure 2

Ground and excited state potentials for partial waves and rotational states up to $l=20$ and $J=21$. Open circles indicate the point of couplings forming a net of Condon points. Here, $\delta =-3{\gamma }_{\mathrm{at}}$. The ground states have been shifted up by the energy of 1 photon.

Figure 3

The field-dressed potentials for the magnesium quasimolecule up to $l=12$ and $J=13$. Here, $\delta =-3{\gamma }_{\mathrm{at}}$ and $I∕I_s=8.0$.