A thermal initiation correction to Shepp's rotating sector theory

Abstract

AbstractShepp's rotating sector theory for determining radical recombination rate constants, kb, has been modified to take account of radical production by a concurrent thermal reaction. A theoretical sector curve expression has been derived which gives the average radical concentration under intermittent illumination as a function of α, the ratio of first‐to second‐order radical removal rates, n, the ratio of thermal initiation to photoinitiation, and β, the ratio of the flash time to the half time of second‐order radical removal. Analysis of the sector curves generated by the modified theory shows that n has a greater effect on kb than α and that the rotating sector method should be applied only to those photochemical systems in which termination by first‐order processes is less than 34% (α = 0.52) and thermal initiation is less than 2% (n = 0.02).