Intracluster reactions in phenylacetylene ammonia clusters initiated through resonant enhanced ionization

Abstract
Protonated ammonia clusters of specific size are observed to form following the resonant enhanced ionization of phenylacetylene–ammonia clusters PA⋅(NH3)n in the 000 region of the S1–S0 transition of the (unclustered) PA. The resonance enhanced absorption of two photons, ≊8.8 eV total energy, are found to cause intracluster reactions for n≥5. The findings imply that the adiabatic ionization potential of (NH3)4 is greater than 8.8 eV, while that of (NH3)5 is (slightly) less.