Laser diagnostics of a potassium plasma using selective excitation spectroscopy

A thermally tuned Q-switched ruby laser has been used to selectively excite the 6939-A transition in a potassium plasma. A burst of intensified spontaneous emission at both 6911 and 6939 A has been observed. This enhanced emission contains information on the local properties of the plasma as demonstrated by the observed dependence of the signal duration upon the free-electron density.