X-ray Free Electron Lasers (FELs) can produce extremely intense and very short pulses, down to below 10 femtoseconds (fs). Among the key applications are ultrafast time-resolved studies of dynamics of matter by observing responses to fast excitation pulses in a pump-probe manner. Detectors with sufficient time resolution for observing these processes are not available. Therefore, such experimen...

We report the quantum efficiency of photoluminescence processes of Er optical centers as well as the thermal quenching mechanism in GaN epilayers prepared by metal-organic chemical vapor deposition. High resolution infrared spectroscopy and temperature dependence measurements of photoluminescence intensity from Er ions in GaN under resonant excitation excitations were performed. Data provide a ...

We have studied the charge capture and impact excitation processes in H+ on He+ collisions over a wide range of collision energies by solving the time-dependent Schrödinger equation with the classical trajectory approximation for the projectile. The time-dependent Schrödinger equation is solved by the split-operator method with a generalized pseudospectral (nonuniform grid) method in the energy...

Nano-structuring can significantly modify the properties of materials. We demonstrate that size-dependent modification of the spin-wave spectra in magnetic nano-particles can affect not only linear, but also nonlinear magnetic response. The discretization of the spectrum removes the frequency degeneracy between the main excitation mode of a nano-particle and the higher spin-wave modes, having t...

We studied the interactions between excitation and inhibition in morphologically identified amacrine cells in the light-adapted rabbit retinal slice under patch clamp. The majority of on amacrine cells received glycinergic off inhibition. About half of the off amacrine cells received glycinergic on inhibition. Neither class received any GABAergic inhibition. A minority of on, off, and on-off am...

Solid argon is a model system for studies of radiative and nonradiative processes associated with electronic excitation by MeV light ion bombardment. The electronic excited states, excitons and excimers, have been extensively studied in this material and careful studies have also been made of the ejection (sputtering) of atoms from the surface. The sputtering requires transfer of energy from el...

The inverse approach from MR images to electrical propagation is very novel, but difficult due to complicated processes from electrical excitation to heart contraction. A novel strategy is presented to recover cardiac electrical excitation pattern from medical image sequences and ECG data. We used MRI images to estimate the current density and visualize it on the surface of the heart model. The...

Remote excitation and emission of two-photon luminescence and second-harmonic generation are observed in micrometer long gold rod optical antennas upon local illumination with a tightly focused near-infrared femtosecond laser beam. We show that these nonlinear radiations are emitted from the entire antenna and the measured far-field angular patterns bear the information regarding the nature and...

We present FUSE observations of the extincted O9.5 star, HD 34078. The 19 first levels of H2 are detected (i.e. from J=0 to v=1, J=5) as well as HD in its two first levels. The excitation of H2 up to J=7 can be explained using a combination of Photon Dominated Region (PDR) and MHD shock models. However, understanding the large amount of H2 found in higher excitation states seems to require more...

We show that background free nonlinear optical imaging of Au nanostructures with a resolution down to 30 nm can be achieved. To attain such performance, an ultrafast laser source (110 fs pulse duration) has been integrated into a parabolic mirror assisted scanning near-field optical microscope. Combining nonlinear hyperspectral imaging and the simultaneously obtained topography, the setup allow...