Optical-optical double resonance (OODR) spectra in the vibrationless S,, So absorption transition of jet-cooled pentacene are reported. Spectral holes as well as resolved and individually assigned single rovibronic OODR-lines corresponding to different selected ground states are observed. The experimental OODR-spectra are in good agreement with calculated spectra using rotational constants which were obtained from a band contour analysis. The accuracy of the rotational constants for the So and Si state was improved in comparison to Heinecke et al. [J. Chem. Phys. 109 (1998) 906]. (C) 2003 Elsevier Science B.V. All rights reserved.