Zero kinetic energy photoelectron study of the naphthalene-Ar van der Waals complex

The naphthalene-Ar van der Waals complex formed in a supersonic jet expansion was studied. Mass-selected multiphoton ionization and zero kinetic energy (ZEKE) photoelectron spectra obtained in the two-color (1 + 1′) ionization scheme are reported. The S1−S0 000 transition in the complex is red-shifted by 15 cm−1 and its adiabatic ionization energy is 65607 cm−1 (± 3 cm−1), 85 cm−1 lower than that of bare naphthalene. Ab initio calculations at the level of second order Møller-Plesset theory give a potential energy minimum for the Ar atom at the distance of 3.4 Å above the center of symmetry of naphthalene and the binding energy of 430 cm−1 for the neutral complex.