A NOVEL FIBER-OPTIC-BASED PUMP-PROBE INSTRUMENT FOR THE ACQUISITION OF KINETIC INFORMATION

A pump-probe instrument is described that utilizes two beams from the same laser and a fiber-optic-based sample cell for low-temperature measurements. The utility of this instrument is demonstrated through an examination of the excited-state kinetics of 2,7-diphenylphenanthrene, for which the rate constant of singlet-to-triplet intersystem crossing is found to be approximately 8 x 10(5) s-1. This molecule is interesting in that it undergoes an unusual rotational conformation change in the triplet state with a rate constant of 2.4 x 10(8) s-1 at 77 K.