Signs alteration of nonlinear refraction of cubane-like shaped clusters from nanosecond to picosecond pulses

The excited-state nonlinear refraction of a novel cubane-like shaped metal cluster MoOS3ICu3(2-Mepy)(3) in DMF solution is studied by using Z-scan mea surement technique with laser pulses of 10 ns and 40 ps pulse width at the wavelength of 532 nm, respectively. For picosecond pulses the compound poss esses a self-focusing property, the positive nonlinear refraction is attrib uted to population transitions among singlet states, while for nanosecond p ulses it exhibits a self-defocusing property and the negative nonlinear ref raction is attributed to population relaxing to triplet states. (C) 2001 El sevier Science B.V. All rights reserved.