k's Blog

My present work is to develop models of organic radiolysis, especially liquid hydrocarbons. Mechanisms, kinetics, and product yields of liquid hydrocarbons following irradiation by heavy ions and fast electrons are determined using scavenging experiments. Today, I’m going to talk about my research work on the Heavy Ion Radiolysis of Liquid Pyridine.

Pyridine is the simplest of all nitrogen hetrocycles. The radiolysis of liquid pyridine leads to pyridine singlet and triplet excited states following the neutralization reactions of the electrons with molecular radical cations. The formation and decay of excited states play important roles in the radiation chemistry of hydrocarbon liquids.

Singlet and triplet excited states yields in the tracks of a heavy ion are different than these of a fast electron because the much higher rate of LET increases the concentration of ion pairs in the ion tracks. A fast electron generates a few ion pairs in close proximity and geminate recombination dominates the decay of the charge species to give singlet excited states. At high LET, the combination reactions of ion pairs is completely random because of the near homogeneous distribution of ion pairs along the particle path. Probabilistic arguments then give the relative production of singlet to triplet excited state formation at 1:3. The increase in local concentrations of triplet excited states may lead to different decomposition pathways and thereby affect final product yields.