Pulse-shaping multiphoton FRET microscopy.

Fluorescence Resonance Energy Transfer (FRET) microscopy is a commonly-used technique to study problems in biophysics that range from uncovering cellular signaling pathways to detecting conformational changes in single biomolecules. Unfortunately, excitation and emission spectral overlap between the fluorophores create challenges in quantitative FRET studies. It has been shown previously that quantitative FRET stoichiometry can be performed by selective excitation of donor and acceptor fluorophores.

Exploring wavepacket dynamics behind strong-field momentum-dependent photodissociation in CH(2)BrI(+).

The ultrafast photodissociation dynamics of CH(2)BrI(+) into CH(2)Br(+) + I is studied using high level ab initio electronic structure calculations in conjunction with integration of the time-dependent Schrödinger equation and compared with measured pump-probe signals. These pump-probe measurements provide evidence for momentum-dependent dissociation, which is interpreted using two theoretical models. The first is based on DFT and TD-DFT calculations neglecting spin-orbit coupling, while the other, more rigorous model employs a larger number of coupled multi-configurational potentials obtained by means of CASSCF calculations.

Molecular fragmentation driven by ultrafast dynamic ionic resonances.

The authors time resolve molecular motion in bound state, ionic potentials that leads to bond cleavage during the interaction with intense, ultrafast laser fields. Resonances in molecular ions play an important role in dissociative ionization with ultrafast laser fields, and the authors demonstrate how these resonances evolve in time to produce dissociation after initial strong-field ionization. Exploiting such dynamic resonances offers the possibility of controlled bond breaking and characterizing time-dependent molecular structure.