10-exo-Fluoro-10'-endo-chlorotricylco[4.3.1.0(1,6)]decadiene-2,4 (1) was synthesized. Continuous photolysis of 1 (300 nm) generates chlorofluorocarbene 2, which can be intercepted with tetramethylethylene (TME) to form the expected cyclopropane 3. Laser flash photolysis (LFP) of 1 (308 nm) in cyclohexane at ambient temperature does not result in the direct detection of 2 by time-resolved UV-vis spectroscopy. However, UP of 1 in the presence of pyridine produces the intense transient absorption of ylide 4 at 450 nm. The absolute rate constant of reaction of 2 with pyridine is 8.0 x 10(9) M-1 s(-1) in cyclohexane. UP (266 nm) of 1 in heptane at ambient temperature produces a transient species with a C-F vibration at 1142 cm(-1) and a lifetime of 2.5 mus at ambient temperature. The carrier of the transient absorption is assigned to carbene 2 on the basis of density functional theory (DFT) calculations and on the basis of its kinetic behavior. The absolute rate constant of reaction of carbene 2 with TME was determined by monitoring the transient absorption of ylide 4 (Freon-113) or by time-resolved IR spectroscopy (heptane) to give values of 1.1 x 10(8) M-1 s(-1) and 2.9 x 10(8) M-1 s(-1), respectively. This is the first measurement of a bimolecular ground-state singlet carbene reaction by both time-resolved UV-vis and IR spectroscopy. The value determined by the time-resolved IR measurement is more accurate than that from the ylide probe technique.