On the Mechanism of Excitation Energy Transfer Involving Long and Short Range Interaction in Dilute Organic Liquid Scintillator Systems

The rate parameter K$\text{}_{3}$ of solvent-solute energy transfer and the rate parameter K$\text{}_{7b}$ for solvent-quencher energy transfer are determined experimentally under ultraviolet excitation for a system Ethyl 1 butyl-2-methyl-5 ethoxycarboxy methoxy indole-3-carboxylate (EBMEC) in a deoxygenated system comprising 1:9 mixture of toluene-cyclohexane as a function of temperature in the range of 20-70°C, using bromobenzene as a solvent quencher. The data is analysed in terms of compact equation formed by combining Voltz et al. and Birks and Conte models. The interaction distance for the energy transfer from the excited solvent to solute molecules and solvent to quencher molecules are determined using this equation. The magnitude of the interaction distance indicates that the excitation energy transfer takes place due to long-range interaction in the case of solvent-solute energy transfer and short-range interaction in the case of solvent quencher energy transfer in dilute systems.