The photolysis of diazomethane at 214 nm in the presence of ethane and propane was studied. Unimolecular decomposition rate constants for the chemically activated molecules propane and n-butane were measured and found to be very pressure dependent. Approximate energy distributions of the chemically activated molecules were derived using a stepwise collisional deactivation model and RRKM rate constants. The results of these calculations suggest that methylene radicals formed by the 214-nm photolysis of diazomethane are highly vibrationally excited when they insert into C-H bonds. If several uncertainties can be overcome, these unimolecular systems can be used to study intermolecular energy transfer.