The initial photoinduced dynamics of thiomethyl p-coumaric acid (TMpCA) in solution has been studied with dispersed time-resolved pump-probe spectroscopy with a ∼100 fs instrument response and extending over a wavelength range of ∼300 to ∼600 nm. TMpCA is a model chromophore for the intrinsic chromophore found in photoactive yellow protein (PYP). Stimulated emission from the chromophore is quenched on a timescale similar to chromophore within the PYP protein. A product state absorption is also observed and is formed earlier than the relaxation of the excited state and that of an observed transient intermediate. © 2003 Elsevier Science B.V. All rights reserved.