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Abstract: The electron energies were measured to investigate the influences of laser intensity and wavelength on the ion charge state distribution of C q + (q =2–4) when benzene clusters were irradiated by 109–1011 W/cm2 nanosecond laser pulses. The results show that the ratios of C q +/C( q −1)+ strongly depend on laser wavelength but slightly on laser intensity. The mean electron energy up to 100eV was measured, which was qualitatively consisted with the ‘multiphoton ionization ignition-inverse bremsstrahlung heating-electron impact ionization’ three-stage model. The screening effects inside clusters can significantly decrease the ionization potentials of C q + and facilitate the formation of multiply charged ions especially at low laser intensity. [Copyright &y& Elsevier]

Cluster assisted photoionization processes of benzene, which was seeded in argon, induced by an intense 25 ns Nd-YAG laser has been studied by means of time-of-flight mass spectrometry. At the laser intensity of 1011 W/cm2, multicharged ions Cq+ (q=2–3) with kinetic energy up to 150 eV were observed in the mass spectra. Strong evidences support that these ions are formed in the Coulomb explosion of multicharged benzene cluster ions. [Copyright &y& Elsevier]