Laser spectroscopic measurements of fine-structure changing cross sections of Ca⁺ and Sr⁺ ions in collisions with He atoms

Producing Ca⁺ and Sr⁺ ions by laser ablation of pure metal samples and detecting their laser induced fluorescences, cross sections of collision induced transitions between fine-structure levels in the 4p ²P_J state of Ca⁺ and the 5p ²P_J state of Sr⁺ due to collisions with He atoms at room temperature (298 K) have been measured. The cross sections determined are σ (Ca⁺:4p ²P_3/2 → 4p ²P _1/2 ) = 1.17 ± 0.05 angstrom², σ(Ca⁺:4p ²P _1/2 → 4p ²P_3/2) = (7.92 ± 0.44) × 10^-1 angstrom² and σ(Sr⁺:5p ²P_3/2 → 5p ²P _1/2 ) = (1.44 ± 0.10) × 10^-2 angstrom².