A NEW PHOTOMETRIC-METHOD FOR DIRECTLY DETERMINING MOLAR ABSORPTIVITY QUANTUM YIELD PRODUCTS OF EXCITED-STATES - APPLICATION TO TRIPLET C-60

A new method is presented for calibrating excited state absorption str engths in terms of absolute densities of excited sample molecules. Bea m-imaging photometry measures the profiles of an excitation laser puls e and a collinear probing beam. From these data plus the ground state absorptivity and the induced absorbance at the probing wavelength, one calculates the product of excited state molar absorptivity and format ion quantum yield. This photometric method involves no comparison to r eference samples. Measurements on the triplet state absorptivity of C- 60 agree closely with recent reports based on comparative methods, sug gesting the validity of both approaches. (C) 1998 Published by Elsevie r Science B.V. All rights reserved.