The Delayed Luminescence of Tryptophan in Aqueous LiCl Solutions at 77 K

S h o z i Y a m a s h i t a a n d G i i t i T o m i t a Institute o f Biophysics , Facul ty o f Agriculture, K y u s h u University, Fukuoka 812, Japan Z. Naturforsch. 34b , 344-349 (1979); received October 17, 1978 Recombinat ion Luminescence, Tryptophan , Trapped Electron The effect o f LiCl on the delayed luminescence caused b y the recombination of photo e jected electrons with t ryptophan cations in aqueous solutions was investigated at 77 K . The luminescence intensity strongly depended on LiCl concentration. A t high LiCl concentrations, the intensity o f the fast decay component o f the recombination fluorescence decreased t o a constant value, whereas that o f the slow decay component inversely increased. The intensity o f the recombinat ion phosphorescence was weak and unchanged in l ow LiCl concentrat ion range but increased steeply above 7 M LiCl. NO3, electron scavenger, quenched bo th the recombination fluorescence and phosphorescence, but the degree of the quenching decreased rapidly in the order o f the fast decay component of the recombination fluorescence, the slow decay component o f the recombination fluorescence, the recombination phosphorescence. Furthermore, the quenching eff iciency of NO3 for each recombinat ion luminescence was f o u n d to diminish with increasing LiCl concentration. The distribution of photo -e jec ted electrons to shallowand deep-traps, dependent on LiCl concentration, was discussed f r o m results obtained.