S₀, S₁, and Ion I₀ Binding Energies of the p-Methoxyphenethylamine(H₂O)₁₋₄ Complexes

Binding or dissociation energies of the ground state, S 0, the first electronic excited state, S 1, and the ion ground state, I 0, of the p-methoxyphenetylamine(H 2 O) 1 - 4 complexes, referred to henceforth as either MPEA(H 2 O) 1 - 4 or by their stoichiometric ratios 1:1−4, have been analyzed by threshold ion fragmentation. MPEA(H 2 O) 1 - 4 complexes were prepared by the supersonic expansion of premixed samples containing appropriate amounts of MPEA and water molecules into carrier gas He. A number of isomers, with characteristic transition energies, have been identified: two for MPEA(H 2 O) 1 at 35 676 and 35 689 cm -1, one for MPEA(H 2 O) 2 at 35 687, one for MPEA(H 2 O) 3 at 35 571 and two for MPEA(H 2 O) 4 at 35 419 and 35 422 cm -1 respectively. The ionization energy and fragmentation thresholds, the latter defined as the onset energy of the process MPEA(H 2 O) n * + h ν→ MPEA(H 2 O) n - 1 + + H 2 O, have been determined, and from them the dissociation energies for the set of MPEA(H 2 O) 1 - 4 isomers in their ground state, first electronic excited states, and ion ground states were readily obtained. The set of values are compared with those computed for the water association complexes.