A recent density matrix treatment of femtosecond photodesorption has been extended to include frequency chirping effects. It describes the dissipative dynamics of desorption and substrate electronic excitations, with an optical Bloch equation and rate equations for the substrate temperature and electron density, including the electron-phonon coupling. Results on CO/Cu(0 0 1) are presented for yield vs. pulse fluence, showing agreement with experimental values, and for chirping effects. Variations of the chirped frequency by +/-5% give large changes in the yields. The calculations suggest that chirping can be used to control desorption yields, and to investigate the strength of electron-phonon coupling in metals. (C) 2003 Elsevier Science B.V. All rights reserved.