Calculations of collisions between cold alkaline-earth-metal atoms in a weak laser field - art. no. 033425

We calculate the fight-induced collisional loss of laser-cooled and trapped magnesium atoms for detunings up to 50 atomic linewidths to the red of the S-1(0)-P-1(1) cooling transition. We evaluate loss rate coefficients due t o both radiative and nonradiative state-changing mechanisms for temperature s at and below the Doppler-cooling temperature. We solve the Schrodinger eq uation with a complex potential to represent spontaneous decay, but also gi ve analytic models for various limits. Vibrational structure due to molecul ar photoassociation is pre-sent in the trap loss spectrum. Relatively broad structure due to absorption to the Mg-2 (1)Sigma (u) state occurs for detu nings larger than about ten atomic linewidths. A much sharper structure, es pecially evident at low temperature, occurs even at smaller detunings due t o Mg-2 (1)Pi (g) absorption, which is weakly allowed due to relativistic re tardation corrections to the forbidden dipole transition strength. We also perform model studies for the other alkaline-earth-metal species Ca, Sr, an d Ba, and for Yb, and we find similar qualitative behavior as for Mg.