Laser spectroscopic measurements of fine structure changing cross sections of alkali earth ions in collisions with molecular hydrogen (H₂, D₂)

Production of alkali earth ions (Ca⁺, Sr⁺ and Ba ⁺) by means of a laser ablation technique and measurement of their laser-induced fluorescence, cross sections of collision-induced transitions between the np ²P_J fine structure levels (n≤ 4, 5 and 6 for Ca⁺, Sr⁺ and Ba⁺, respectively) due to collisions with hydrogen molecules at room temperature (298 K) has been performed. The cross sections thus determined for the collisions with H ₂ and D₂ are σ(Ca⁺: 4p ²P _3/2 → 4p ²P_1/2) ≤ 20.5 0.5, 27.1 1.3 ², σ(Ca⁺: 4p ²P_1/2→ 4p ²P_3/2) ≤ 13.2 0.6, 18.7 0.8 ², σ(Sr⁺: 5p ²P_3/2→ 5p ²P_1/2) ≤ 22.7 0.4, 18.0 0.4 ² and σ(Ba⁺: 6p ²P_3/2→ 6p ²P_1/2) ≤ 10.4 0.1, 3.4 0.2 ², respectively.