Photoionization of tris(2-phenylpyridine)iridium

摘要

The photoionization of gas-phase tris(2-phenylpyridine)iridium (Ir(ppy) 3) has been examined. One- and two-photon studies yield a conservative estimate for the upper bound to the ionization energy of 6.4eV. The one-photon experiment used 193nm radiation. The latter experiments used tunable UV radiation to excite the ligand-centered ~1LC state, which is followed by radiationless decay and photoionization. An accompanying paper presents a theoretical study of excited singlets and triplets and low-energy states of. The calculated ionization energy is 5.9eV. The experimental and calculated results together indicate an ionization energy of 6eV. An undulation in the ion yield spectrum (270cm ~1 spacing) was observed. It is due to structure in the transition that originates from T _1, which is populated through radiationless decay of ~1LC. At low fluence, is produced without fragmentation, despite the fact that a large amount of vibrational energy is present in T _1. Specifically, this vibrational energy is the sum of and the thermal energy due to the 177 Ir(ppy) _3 vibrational degrees of freedom at 500K, i.e. the temperature at which the experiments were carried out. This vibrational energy is transported efficiently to the cation.