Abstract: Gas-phase thermolysis of 2, 3-diazabicyclo [2.1. l] hex-2-ene (1) produces highly vibrationally excited (chemically activated) bicyclo [1.1. O] butane (2). The excited 2 rearranges to butadiene, in competition with collisional deactivation by a bath gas. Quantitative modeling using RRKM theory and a stepladder model for collisional deactivation indicates that, of the substantial amount of excess energy available to the ...