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Coulomb explosion of hexa-fluorobenzene in an intense laser field (1.0 × 10 16 W cm −2 ) was investigated using time-of-flight (TOF) mass spectrometry. The fluorine ions were mainly ejected parallel to the laser polarization, whereas the carbon ions were broadly distributed. The angular distribution features were totally different from those of benzene. Molecular dynamics simulations indicated that the substitution of fluorine atoms and/or ions caused ultrafast deformation of the carbon framework during the explosion. The effect of molecular alignment induced by the intense laser field is discussed.

Two pairs of organic molecules (2,3-dimethyl-1,3-butadiene, 2,5-dimethyl-2,4-hexadiene; 1,4-cyclohexadiene, 1,3-cyclohexadiene) were irradiated with a high-intensity 120-fs laser pulse in the intensity region of 10 14 W cm −2 . One molecule in each pair had no allowed electronic transition in the cation at the excitation wavelength of 800 nm, resulting in parent ion dominance. In contrast, the counter molecule, which had a similar structure but with absorption in the cation at the excitation wavelength, showed heavy fragmentation with a negligibly small signal of the parent ion. The previously reported observations are explainable on the basis of the proposed mechanism for fragmentation in femtosecond ionization.

C 60 vapor was irradiated with an intense femtosecond laser pulse (1.0×10 16 W/cm 2 in 100 fs at a wavelength of 790 nm). Multiply charged ions, assignable up to C 60 4+ , were observed in the time-of-flight spectra, while C 60 q + ( q ≤2) with many fragments were detected by a nanosecond laser pulse (1.2×10 13 W/cm 2 in 9 ns at 532 nm). The formation of the multiply charged ions will be explained in terms of barrier suppression ionization (BSI) for the case of femtosecond excitation.

Two-photon absorption has been found to induce the photoreduction of Eu 3+ to Eu 2+ in methanol solution of EuCl 3 . The excitation spectra clearly indicate that the photoreduction occurs via a 4f′ ←4f transition. The second photon is presumed to be absorbed in a transition band of an intermediate level to a charge-transfer level. The reduction efficiency was about 3 × 10 −5 for the excitation at 464.7 nm under 460 mJ/cm 2 .

Quantum yields of hydrated electrons of Cl−, Br−, I−, SO2−4, SCN− and OH− in aqueous solution have been determined by means of 193 nm laser flash photolysis. Shorter wavelength excitation showed higher quantum yields for I− and SCN− ions in three wavelengths of 193, 222 and 248 nm. The highest yield was 0.73 for SO2−4 at 193 nm and the lowest one was 0.015 for SCN− at 248 nm.