Hole Burning in the Organic Triplet State: Side Holes in an Amorphous Glass

Abstract

Hole-burning spectroscopy has been widely applied to the S0-S1 transition of organic molecules in amorphous hosts [1-3]. However, only very few reports on the hole-burning spectroscopy of the triplet state have appeared [4,5]. The low oscillator strength of the S0-T1 transition is the obvious handicap in performing such experiments. The oscillator strength of the S0-T1 transition can be dramatically increased by the heavy atom effect [6] making hole-burning experiments in the S0-T1 transition more feasible. A very pronounced heavy atom effect can be expected in ligand-centred singlet -triplet transitions of second and especially third row transition metal complexes leading to lifetimes in the μs range.