The photoexcited aqueous fullerene (C 60 ) suspension was shown to exhibit an asymmetric photoluminescence (PL) spectrum, which, different from the symmetric spectrum observed previously in C 60 solutions or suspensions, still stems from the characteristic phosphorescence of singlet oxygen (O 2 (a 1 Δ)) owing to its dependence on oxygen concentration. In contrast to the microsecond-level lifetime of O 2 (a 1 Δ) in water solutions, that in our C 60 suspensions was measured at room temperature to be relatively long, about 2−3 ms, which is ∼1000 times longer than the value reported by Bilski et al. The physical mechanism for the asymmetric O 2 (a 1 Δ) PL from C 60 suspensions was studied in depth, indicating that it in fact originates from O 2 molecules trapped in the C 60 lattice within the suspended C 60 aggregates (nC 60 ). This mechanism, which can explain well our above results, was further validated by the nC 60 's high-resolution transmission electron microscopy (HRTEM) images with lattice fringes and the experimental temperature dependence of O 2 (a 1 Δ) lifetimes in nC 60 suspensions. Our findings suggest that the bulk-phase O 2 (a 1 Δ) in aqueous nC 60 suspensions results from the diffusion of the O 2 (a 1 Δ) generated within the interior of nC 60 aggregates.

We report a study on resonance enhanced multiphoton ionization photoelectron spectroscopy (REMPI-PES) involving the fast predissociative state of ammonia, using A 3 nano-and femtosecond lasers. The multiphoton scheme involves (1 ] 1), (2 ] 2), (2 ] 2) ] 1 and (2 ] 2) ] 2 photon processes. We have found a progression of stretching vibrations in the PE spectrum when pumping 1 and 3 as intermediateThe stretching vibration intensity distributions in the photoelectron spectrum are calculated by using the Chebychev method of the wavepacket propagation. The femtosecond spectrum shows a similar feature to the nanosecond spectrum. However, high laser power also causes band broadening and shifting e †ect as well as above threshold multiphoton ionization.

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