Simulating Real-Time Molecular Electron Dynamics Efficiently Using the Time-Dependent Density Matrix Renormalization Group.

Compared to ground-state electronic structure optimizations, accurate simulations of molecular real-time electron dynamics are usually much more difficult to perform. To simulate electron dynamics, the time-dependent density matrix renormalization group (TDDMRG) has been shown to offer an attractive compromise between accuracy and cost. However, many simulation parameters significantly affect the quality and efficiency of a TDDMRG simulation.

Attochemistry Regulation of Charge Migration.

Charge migration (CM) is a coherent attosecond process that involves the movement of localized holes across a molecule. To determine the relationship between a molecule's structure and the CM dynamics it exhibits, we perform systematic studies of para-functionalized bromobenzene molecules (X-CH-R) using real-time time-dependent density functional theory. We initiate valence-electron dynamics by emulating rapid strong-field ionization leading to a localized hole on the bromine atom.

High speed and high resolution table-top nanoscale imaging.

We present a table-top coherent diffractive imaging (CDI) experiment based on high-order harmonics generated at 18 nm by a high average power femtosecond fiber laser system. The high photon flux, narrow spectral bandwidth, and high degree of spatial coherence allow for ultrahigh subwavelength resolution imaging at a high numerical aperture. Our experiments demonstrate a half-pitch resolution of 15 nm, close to the actual Abbe limit of 12 nm, which is the highest resolution achieved from any table-top extreme ultraviolet (XUV) or x-ray microscope.

Influence of detector noise in holographic imaging with limited photon flux.

Lensless coherent diffractive imaging usually requires iterative phase-retrieval for recovering the missing phase information. Holographic techniques, such as Fourier-transform holography (FTH) or holography with extended references (HERALDO), directly provide this phase information and thus allow for a direct non-iterative reconstruction of the sample. In this paper, we analyze the effect of detector noise on the reconstruction for FTH and HERALDO with linear and rectangular references.

Subcycle-resolved probe retardation in strong-field pumped dielectrics.

The response of a bulk dielectric to an intense few-cycle laser pulse is not solely determined by the pulse envelope, but also by ultrafast processes occurring during each optical cycle. Here, a method is presented for measuring the retardation of a probe pulse in a strong-field pumped, bulk dielectric with subcycle resolution in the pump-probe delay. Comparisons to model calculations show that the measurement is sensitive to the timing of the electronic Kerr response.