Laser desorption followed by jet cooling has been used to produce an intense beam of internally cooled benzoic acid monomers. As a result, the S1 ← S0 gas-phase absorption spectrum of the jet-cooled benzoic acid monomer could be identified for the first time. Delayed ionization out of a triplet state, populated by rapid S1 → T intersystem crossing, followed by mass-selective detection of the parent ions is performed. The spectral lines have a Lorentzian shape with a line width of 6.5 cm-1, corresponding to an intersystem crossing rate of 1.2 × 1012 s-1. © 1990 American Chemical Society.