Collision-Induced Mixing in the First Excited States of Sodium and Potassium

The cross sections for the collision-induced transfer of excitation from the ${}_{}{}^2{}_{}{}^{}P_{\frac{3}{2}}^{}{}_{}{}^{}$ level to the ${}_{}{}^2{}_{}{}^{}P_{\frac{1}{2}}^{}{}_{}{}^{}$ level of the first excited states of the alkali atoms have been measured for several alkali-noble gas systems. The cross sections were determined with a conventional resonance fluorescence technique in which the radiation from a spectral source was absorbed and re-emitted by an alkali vapor at low pressure (∼${10}^{-6\mathrm{}}$ Torr), and the scattered light analyzed with a scanning spectrometer. Provision was made for the introduction of various noble gases at controlled pressures into the alkali vapor. The determined cross sections are (in units of ${10}^{-16\mathrm{}}$ ${\mathrm{cm}}^2$): Na-He, 41.1±2.9; Na-Ne, 36.1±2.5; Na-Ar, 64.6±5.2; Na-Kr, 68.2±5.5; Na-Xe, 61.8±4.9; K-He, 52.8±5.8; K-Ne, 14.0±1.2; K-Ar, 34.0±3.1. The quoted errors are estimated 70% confidence intervals. The measurements are compared with other experimental results and with various estimated cross sections.