We propose a formulation of an absorbing boundary for a quantum particle. The formulation is based on a Feynman-type integral over trajectories that are confined by the absorbing boundary. Trajectories that reach the absorbing wall are instantaneously terminated and their probability is discounted from the population of the surviving trajectories. This gives rise to a unidirectional absorption ...

In the Jager group, a series of bichromophoric light-harvesting antenna systems has been synthesized in a modular fashion by covalent attachment of blue light-absorbing naphthalene monoimide energy donors to green light-absorbing perylene3,4,9,10-tetracarboxylic acid energy acceptors. Quantitative and ultrafast (ca. 1 ps) intramolecular excitation energy transfer (EET) from the donor to the acc...

A novel fluorescence resonance energy transfer (FRET) system containing a two-photon absorbing dye and a nile red chromophore has been synthesized. Upon two-photon excitation by laser at 815 nm this molecule displays efficient energy transfer from the two-photon absorbing dye to the nile red moiety, with an 8-fold increase in emission compared to the model compound. Similarly, single-photon exc...

We study sandpile models as closed systems, with the conserved energy density zeta playing the role of an external parameter. The critical energy density zeta(c) marks a nonequilibrium phase transition between active and absorbing states. Several fixed-energy sandpiles are studied in extensive simulations of stationary and transient properties, as well as the dynamics of roughening in an interf...