Polarization spectra of excited-state-Mg(3p)–rare-gas-atom optical collisions

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Abstract
Experimental, polarization-dependent excitation spectra for excited-state-Mg–rare-gas-atom optical collisions are reported. In these first studies of the process, polarized Mg atoms in the 3p 1 P1 level are produced by absorption of linearly polarized light tuned to the 3s 1 S0→3p 1 P1 resonance transition at 285.2 nm. Detuning-dependent, collision-induced polarization spectra are measured in a ±200-cm−1 range around the Mg 3p 1 P1→5s 1 S0 transition at 571.2 nm. The spectra correspond to probing transient Mg-Ne and Mg-Ar molecules on 3p Π11→5s Σ0+1 and 3p Σ0+1→5s Σ0+1 electronic transitions. Measurements of these excited-state polarization spectra for Mg-Ne optical collisions reveal that for detunings to the red of the atomic Mg 3p 1 P1→5s 1 S0 transition, electronic linear polarization greater than 50% survives far into the molecular regime. This represents a direct measure of the polarization important to alignment-dependent inelastic processes in alkaline-earth-metal–rare-gas-atom collisions. The polarization spectra are discussed in terms of existing information on the interatomic potentials and through an axial recoil limit for the polarization degree for parallel and perpendicular molecular transitions. Rate coefficients k for disalignment of Mg 3p 1 P1 atoms by collisions with Ar [k=9.4(5)×10−10 cm3/s] and with Ne [k=6.5(7)×10−10 cm3/s] are also extracted from the data.