Oxygen Effect and Temperature Dependence of Fluorescence Intensity in Naphthalene Scintillators

Abstract

In solution scintillators with molten naphthalene as a solvent, fluorescence quenching by dissolved oxygen and the temperature dependence of light output are studied with excitation by gamma-rays and uv lights. The fluorescent solutes are PPO, BBO, POPOP, QP, DPH and DPS. Dissolved oxygen can be removed rapidly by bubbling nitrogen. Quenching by oxygen is shown to be in competition with energy transfer from solvent to solute. It may be estimated that the lifetime of excited molecules in molten pure naphthalene is increased to almost twice by removal of oxygen. The bubbling of nitrogen increases the fluorescence intensities of practical solutions by 20–40%. The negative temperature coefficients of light output of naphthalene solutions are 2–7×10-3/°C independent of excitation modes. The fluorescence intensities of the solutions equilibrated with air remain almost constant over the temperature range of 80–130°C.