Oscillator Strengths of Ca II, Sr II, and Ba II

The lifetimes of the 5p²P₃₂ and 5p²P₁₂ states of Sr⁺ and the 6p²P₃₂ and 6p²P₁₂ states of Ba⁺ have been measured by the Hanle-effect technique with optical excitation from the ion ground state. (The lifetimes of the Mg⁺ 3p²P₃₂ and Ca⁺ 4p²P₃₂ states were obtained by the same technique and reported previously.) These Ca⁺, Sr⁺, and Ba⁺ states each decay to a ²D_32,52 doublet as well as to the ground ²S₁₂ state, and the branching ratios for these transitions have been measured. The ions were produced by introducing traces of the atomic vapor into an argon discharge. Consequently, the cross sections for collisional depolarization of these ²P_J states due to collisions with argon were also obtained from the measurements. The experimental results are given in Tables I and II. A discussion of the ion-atom collisional depolarization cross sections is included.