The ring-opening reaction of trithianes possessing aromatic substituents has been studied using femto-second broadband UV-Vis transient absorption spectroscopy. Photocleavage of the CAS bond occurs during the short-lived (1.5 ps) singlet excited state of trithiane. The products are formed with excess of vibrational energy and cooling of the hot molecules occurs with a 12.1 ps time constant in acetonitrile. (c) 2008 Elsevier B.V. All rights reserved.