Ionization of naphthalene via the Rydberg states using a femtosecond 775 nm pulse

Photoelectron spectroscopic studies on naphthalene excited with a femtosecond 775 nm laser pulse reveal two ionization paths via the Rydberg states: a resonance-enhanced, non-relaxed process and one that goes through internal conversion of an undetermined intermediate. Varying the pulse duration with several hundred femtosecond causes only small change in the spectra. Compared to the ionization mechanism of anthracene, the reduced molecular size changes the ionization behavior due to a slower internal conversion rate and the presence of atomic-like Freeman resonances.