Testing the fate of nascent holes in CdSe nanocrystals with sub-10 fs pump-probe spectroscopy.

Numerous studies have reported that transient absorption spectra in core CdSe nanocrystals do not register state filling in 1Sh, an absence which has profound consequences in light-emitting applications. It has been assigned alternatively to rapid hole trapping, or to distribution over a dense degenerate valence band manifold which includes dark states. Here we attempt to observe early contributions of nascent holes to the bleaching of the band edge exciton transition by conducting 1Se1Sh pump-1Se1Sh probe spectroscopy with <10 fs laser pulses on organic ligand passivated CdSe crystals.

The elusive dynamics of aqueous permanganate photochemistry.

Despite decades of investigation, mechanistic details of aqueous permanganate photo-decomposition remain unclear. Here we follow photoinduced dynamics of aqueous permanganate with femtosecond spectroscopy. Photoexcitation of KMnO(aq) in the visible unleashes a sub-picosecond cascade of non-radiative transitions, leading to a distinct species which relaxes to S with a lifetime of 16 ps.