Femtosecond dynamics of cyclopropenylidene, c-C3H2

The photophysics of the B 1B1 state of isolated cyclopropenylidene, c-C3H2, has been studied by femtosecond time-resolved photoionisation and photoelectron spectroscopy. The carbene was produced by flash pyrolysis of 3-chlorocycloprop-1-ene. The bands at 266.9 nm and 264.6 nm have been investigated. The excited state deactivates in a two step process. The first time constant of less than 50 fs corresponds most likely to a nonradiative transition to the A-state, the second one on the order of 200 fs describes the internal conversion to the electronic ground state. The data are compared to those measured for the chlorinated carbene c-C3HCl. In the photoelectron spectrum of c-C3H2 resonances were observed which can be assigned to members of a Rydberg d-series.