SIZE-EFFECTS ON ENERGY RELAXATION AND EXCITED-SPECIES DESORPTION IN KRYPTON CLUSTERS - FLUORESCENCE LIFETIME MEASUREMENTS WITH 10 EV LASER EXCITATION

Fluorescence lifetime measurements of Kr-N clusters ((N) over bar=2-20 00) have been carried out using intense 10 eV laser excitation near P- 3(2), metastable atomic energy level. Two principal groups of electron ically excited dimers Kr-2 have been found in desorption: dimers, loo sely bound near the (P-3(2)+S-1(0)) dissociation limit, ejected from c ooled clusters and dimers undergoing vibrational relaxation from hot c lusters. The desorption is principally terminated when (N) over bar gr eater than or equal to 50 at./cluster. The relaxation kinetics seems t o converge to the properties of a solid state for 10(2) less than or e qual to (N) over bar less than or equal to 10(3) at./cluster. A variat ion of the Kr-2(1(u)/0(u)(-)) radiative lifetime, from 264 ns (in gas phase) to 440 ns ((N) over bar=10(2)), has been found, An equilibrium cluster temperature of 57 K has been calculated from this I(N) depend ence. (C) 1997 American Institute of Physics.