Dissociation energetics of the phenol(+)center dot center dot center dot Ar-2 cluster ion: The role of pi -> H isomerization

The dissociation energetics in the phenol(+)center dot center dot center dot Ar-2(2 pi) 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 similar to 210 and similar to 1115 cm(-1), respectively. The difference between the appearance energy for the first Ar ligand in phenol(+)center dot center dot center dot Ar-2(2 pi) and the dissociation energy of the phenol(+)center dot center dot center dot Ar(pi) dimer (535 cm(-1)) is explained by the isomerization of one pi-bound Ar ligand to the OH binding site (H-bond) upon ionization. The energy difference between phenol(+)center dot center dot center dot Ar-2(2 pi) and phenol(+)center dot center dot center dot Ar2(H/pi) could also be estimated to be around 325 cm(-1), which corresponds roughly to the difference of the binding energy of a pi-bound and H-bound Ar ligands. The binding energy of the H-bound Ar atom in phenol(+)center dot center dot center dot Ar-2(H/pi) is derived to be similar to 905 cm(-1). (C) 2010 American Institute of Physics. [doi:10.1063/1.3482733]