Temperature dependence of the phosphorescence lifetime of benzene and n-alkylbenzenes between 4.2 and 100.deg.K

Abstract

The temperature dependence of the phosphorescence lifetime of benzene and its n-alkyl derivatives CeH5CnH2n+1, = 1 to 13, has been measured in a rigid glass of a mixture of methylcyclohexane-isopentane (4:1 by volume) between 4.8 and 100°K. The phosphorescence lifetime is temperature independent below about 60°K, depending on the solute, and temperature dependent in a relatively small temperature range at higher temperatures. Arrhenius plots indicate that in this region there are two or more paths of externally influenced nonradiative decay contributing to the decay of the triplet state. The incoherence in previously reported data of phosphorescence lifetimes at 77°K of a specific molecule can be attributed to temperature and solvent effects while those at 4.2°K can be attributed solely to solvent effects. The phosphorescence lifetimes of the n-alkylbenzenes depend on the chain length of the alkyl substituent, but no simple relation to other molecular parameters has been found.

Local dielectric response in 1-propanol: α-relaxation versus relaxation of mesoscale structures

“…17 While its origin is still debated, the effect in itself has been known for a long time for different phosphorescent dyes like naphthalene, benzene, toluene and several other aromatic molecules dissolved in various solvents. [21][22][23][24][25][26][27] Some authors attributed the temperature dependence of the phosphorescence lifetime to radiative and nonradiative decays, [21][22][23][24][25][26] while other authors linked this effect to the solvents microviscosity. 27 In any case, this temperature dependence of the phosphorescence lifetime can be as much a limitation as an advantage for TSD experiments.…”

Excited States and Reactions in Liquids

“…They find that the phosphorescence lifetimes of toluene and toluene ada vary a little with temperature over the range 42°K to 77°K and also with the type of glass used. Leubner (99) at 77°K, provided the glass has had sufficiEmt time to achieve thermal equi librium. Morantz & Martin (100) do find variations in the phosphorescence lifetimes of molecules in different glasses and crystalline materials at 77°K, which they attribute to a change in the radiationless transiti on processes with the packing of various materials.…”