Multiphoton ionization and dissociation of naphthalene at 266, 355, and 532 nm

A comparison of laser-induced multiphoton ionization/dissociation and dissociation/ionization pathways of naphthalene, C10H8, is presented at 266, 355, 532 nm, using time-of-flight mass spectrometry, ToF-MS. From the spectra several processes were identified: molecular ionization, simple dissociation, hydrogen transposition, hydrogen loss, and total deprotonation. The dependence on the wavelength and the radiation intensity is clear. At 266 nm energies per pulse, <1.0 mJ (9.23 × 102 MW cm−2), C10H8+ dominates the spectra and new ions were observed as the laser intensity was increased. At 355 nm, hydrogen loss was the principal dissociative route, with the formation of low mass ions: CHn+, 0 < n < 6, in particular CH6 was identified by isotopic analysis. At 532 nm, the CnHm+ ions, 2 < n < 5, were the most abundant species. The calculated numbers of absorbed photons along with previous calculations were used to propose different fragmentation channels.