The radicals formed in the flash photolysis of 2-methylbut-1-ene and subsequent reactions have been investigated by kinetic spectroscopy and gas liquid chromatography. Less than 10% of photo products are formed by a molecular made of fission of the excited olefin, and of the radical modes the relative probabilities of band fission, β (CH): β (CH): α (CC) are 13: 1.37: 1. The extinction coefficients of β-methallyl radical measured experimentally for all ...