Collisional quenching of Xe+(2 P ) and He 23 S metastables by calcium and strontium metal vapors

Excitation-transfer cross sections have been measured for Penning and charge-transfer reactions in He-Ca, He-Sr, Xe-Ca, and Xe-Sr discharges. In low-current low-pressure discharges of helium, excitation transfer to ionic levels of calcium and strontium was found to be dominated by collisions with 23S helium metastables with measured cross section σ (He 23S–Ca) =4.1×10−15 cm2 and σ (He 23S–Sr) =1.6×10−15 cm2. In xenon discharges, charge-transfer cross sections between xenon ions and calcium and strontium atoms, σ (Xe+-Ca) and σ (Xe+-Sr), were measured to be 2.2×10−16 and 2.3×10−16 cm2, respectively.