On The Temperature Dependace Of The Recombination Fluorescence Of Photoionised Tryptophan In Aqueous Glasses: Consequences Of Electron Tunneling.

The recombination fluorescence seen when tryptophan in ethylene glycol/water and 9m LiCl frozen aqueous glasses is photoionised had been investigated. It is found that the intensity as well as the initial decay rate of this recombination fluorescence decreases as the UV radiation temperature increases from 77K. This is interpreted in terms of a tunnelling process in which the electron trap depth increases slightly with increasing irradiation temperature. This causes the tunnelling rate constant to decrease and as the trap depth drops below the lowest singlet level of tryptophan and increasing fraction of the recombination events will lack the energy necessary to generate recombination fluorescence.