Broadening and shift of the magnesium intercombination line and first triplet line due to the presence of the noble gases

We have employed a two-laser double-resonance method to measure, for the first time, the broadening and shift of the Mg i intercombination line (3s3p ${}_{}{}^3{}_{}{}^{}P_1^{}{}_{}{}^{}$–3$s^2$ ${}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}$) and first triplet (3s4s ${}_{}{}^3{}_{}{}^{}S_1^{}{}_{}{}^{}$–3s3$p^3$ $P_2$) transition due to the presence of helium, neon, argon, krypton, and xenon. Our measurements were performed at pressures below 1 atm. A semiclassical impact theory interpretation of our experimental cross sections provides insight into the nature of the interaction potentials between the two pairs of levels and the noble gases. Our results can be explained in terms of attractive dispersive forces and short-range repulsive forces. A comparison is made between the Mg i broadening and shift cross sections and cross-sectional data of intercombination lines of other alkaline-earth elements and resonance transitions of alkali-metal vapors.