Dissociation energetics of the phenol+⋯Ar2 cluster ion: The role of π→H isomerization

The dissociation energetics in the phenol+⋯Ar2(2π) cluster ion have been investigated using photoionization efficiency and mass analyzed threshold ionization spectroscopy. The appearance energies for the loss of one and two Ar atoms are determined as ∼210 and ∼1115 cm−1, respectively. The difference between the appearance energy for the first Ar ligand in phenol+⋯Ar2(2π) and the dissociation energy of the phenol+⋯Ar(π) dimer (535 cm−1) is explained by the isomerization of one π-bound Ar ligand to the OH binding site (H-bond) upon ionization. The energy difference between phenol+⋯Ar2(2π) and phenol+⋯Ar2(H/π) could also be estimated to be around 325 cm−1, which corresponds roughly to the difference of the binding energy of a π-bound and H-bound Ar ligands. The binding energy of the H-bound Ar atom in phenol+⋯Ar2(H/π) is derived to be ∼905 cm−1.