The kinetics of the self reaction of neopentyl radicals ((CH3)(3)CCH2) was studied by laser photolysis/photoionization mass spectroscopy. Overall rate constants were obtained in direct real-time experiments in the temperature region 300-500 K and at bath gas densities of (3.00-12.0) x 10(16) molecule cm (3). The observed overall neo-C5H11 + neo-C5H11 rate constants demonstrate negative temperature dependence: k(1) = 3.1 x 10 (12) exp(+ 506 K/T) cm(3) molecule (1) s (1), with estimated uncertainty of 17% over the 300-500 K temperature range. Formation of C10H22 (mass to charge ratio of 142, interpreted as 2,2,5,5-tetramethylhexane) as the primary product of neopentyl self reaction was observed. (C) 2011 Elsevier B. V. All rights reserved.