Technique by which high concentrations of excited states are generated in a jet, permitting the readily determination of spectroscopic properties of those states.
Source:
PAC, 2007, 79, 293. 'Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)' on page 363 (https://doi.org/10.1351/pac200779030293)