S-0, S-1, and ion I-0 binding energies of the p-methoxyphenethylamine(H2O)(1-4) complexes

Binding or dissociation energies of the ground state, S-0, the first electr onic excited state, S-1, and the ion ground state, I-0, of the p-methoxyphe netylamine(H2O)(1-4) complexes, referred to henceforth as either MPEA(H2O)( 1-4) or by their stoichiometric ratios 1:1-4, have been analyzed by thresho ld ion fragmentation. MPEA(H2O)(1-4) complexes were prepared by the superso nic expansion of premixed samples containing appropriate amounts of MPEA an d water molecules into carrier gas He. A number of isomers, with characteri stic 0(0)(0) transition energies, have been identified: two for MPEA(H2O)(2 ) at 35 676 and 35 689 cm(-1), one for MPEA(H2O)(2) at 35 687, one for MPEA (H2O)(3) at 35 571 and two for MPEA(H2O)(4) at 35 419 and 35 422 cm(-1) res pectively. The ionization energy and fragmentation thresholds, the latter d efined as the onset energy of the process MPEA(H2O)(n)* + hv--> MPEA(H2O)(n -1)(+) + H2O, have been determined, and from them the dissociation energies for the set of MPEA(H2O)(1-4) isomers in their ground state, first electro nic excited states, and ion ground states were readily obtained. The set of values are compared with those computed for the water association complexe s.