Fate of Deposited Energy Ionization, Dissociation, Transfer, and Luminescence

Chapter 3 Structure of Charged Particle Tracks in Condensed Media 

Excited states of hydrocarbon molecules often undergo nondissociative transformation, although dissociative transformation is not unknown. In the liquid phase, these excited states are either formed directly or, more often, indirectly by electron-ion or ion-ion recombination. In the latter case, the ultimate fate (e.g., light emission) will be delayed, which offers an experimental window for discrimination. A similar situation exists in liquid argon (and probably other liquefied rare gases), where it has been estimated that -20% of the excitons obtained under high-energy irradiation are formed directly and the rest by recombination (Kubota et al., 1976). 

Excited states of a typical organic molecule can undergo various radiative and nonradiative transformations as follows  

Internal conversion—that is, without change of multiplicity—to the lowest singlet, or to the ground state (Sn—or S0) 

Intersystem crossing—that is, with a change in multiplicity (S2— T1 or 

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Fate of Deposited Energy Ionization, Dissociation, Transfer, and Luminescence... 

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