The paper describes the experimental investigation of a subclass of quartet levels of the alkali-metal atoms which retain metastability against autoionization and have large radiative yields. Using high-pulsed-power microwaves, we obtain emission spectra of Na, K, Rb, and Cs. In each case, the neutral emission spectrum is dominated by emission from these levels.

• Received 7 November 1986

DOI:https://doi.org/10.1103/PhysRevA.35.2095