An apparatus has been developed for the study of the afterglow of a rare-earth spark with a time resolution of 0.1 µsec. A hydrogen thyratron controls a rapidly firing spark gap and the spectrum of the afterglow is recorded with pulsed photomultipliers and ratio techniques. Tests with preseodymium have shown that it is possible to separate lines according to the ion of origin for the second, third, and fourth spectra, according to configuration of origin in the third spectrum of praseodymium, for example, the emission lines of the 4ƒ<sup>2</sup>6<i>p</i>-4ƒ<sup>2</sup>6<i>s</i> and 4ƒ<sup>2</sup>5<i>d</i>-4ƒ<sup>3</sup> transitions. In the case of the 4ƒ<sup>2</sup>5<i>d</i>-4ƒ<sup>3</sup> transition, some terms of the 4ƒ<sup>2</sup>5<i>d</i> configuration are indicated from the more intense lines. The methods developed with praseodymium have been applied to neodymium, and some preliminary results are reported.
W. A. Hovis, JR., "Time-Resolved Spectra of Rare-Earth Ions," J. Opt. Soc. Am. 52, 649-651 (1962)