Crossed-Beam Studies of Aluminum Atom Cooling via Inelastic Collisions with O2 molecules

The pioneering works have demonstrated that the method of single collisions in crossed molecular beams is an important technique for achieving kinetic cooling of atoms or molecules in specific rotational states. In this study, we investigated the elastic and inelastic collisions between Al(2P1/2) metal atoms and O2 molecules at high collision energies in the range of 6.4-14.8 kcal/mol, utilizing the laser-ablation crossed beams in conjunction with time-sliced ion velocity map imaging technique. We observed kinetic cooling of Al(2P1/2) atoms with an upper-limit laboratory-frame root-mean-square velocity of 24 ± 3 m/s, corresponding to a translational temperature of 0.9 ± 0.2 Kelvin in the laboratory frame, facilitated by the vibrational excitation of O2 (v’ = 1) in inelastic collisions. The translational cooling of Al atoms in the lab frame enhances detection probability in the transformation of density-to-flux, as evidenced in the scattering images obtained during the experiments.