Free electron laser induced processes in thin molecular ice

Intermolecular reactions in and on icy films on silicate and carbonaceous grains constitute a major route for the formation of new molecular constituents in interstellar molecular clouds. In more diffuse regions and in protoplanetary discs, energetic radiation can trigger reaction routes far from thermal equilibrium. As an analog of interstellar icecovered dust grains, highly oriented pyrolytic graphite HOPG covered with D2O, NO, and H atoms is irradiated by ultrashort XUV pulses and the desorbing ionic and neutral products are analysed. The yields of several products show a nonlinear intensity dependence and thus enable the elucidation of reaction dynamics by two pulse correlated desorptio

HGHG Scheme for FLASH II

FLASH II is a major extension of the existing FLASH facility at DESY. It has been proposed in collaboration with the Helmholtz Zentrum Berlin HZB . FLASH II is a seeded FEL in the parameter range of FLASH. The final layout of the undulator section of FLASH II allows for different seeding schemes. So that seeding with an HHG source as well as seeding in cascaded HGHG scheme and several combination of these schemes are possible. However, for the shortest wavelengths down to 4 nm the cascaded HGHG scheme is considered. It consists of two frequency up conversion stages utilizing a Ti Sa laser based seeding source in deep UV range. We present and discuss start to end simulation studies for the shortest wavelength generated in the HGHG cascade of FLASH I

Phonon anharmonicities and ultrafast dynamics in epitaxial Sb2Te3

In this study we report on the investigation of epitaxially grown Sb2Te3 by employing Fourier-Transform transmission Spectroscopy (FTS) with laser-induced Coherent Synchrotron Radiation (CSR) in the Terahertz (THz) spectral range. Static spectra in the range between 20 and 120 cm−1 highlight a peculiar softening of an in-plane IR-active phonon mode upon temperature decrease, as opposed to all Raman active modes which instead show a hardening upon temperature decrease in the same energy range. The phonon mode softening is found to be accompanied by an increase of free carrier concentration. A strong coupling of the two systems (free carriers and phonons) is observed and further evidenced by exciting the same phonon mode at 62 cm−1 within an ultrafast pump-probe scheme employing a femtosecond laser as pump and a CSR single cycle THz pulse as probe. Separation of the free carrier contribution and the phonon resonance in the investigated THz range reveals that, both damping of the phonon mode and relaxation of hot carriers in the time domain happen on the same time scale of 5 ps. This relaxation is about a factor of 10 slower than expected from the Lorentz time-bandwidth limit. The results are discussed in the framework of phonon scattering at thermal and laser induced transient free carriers

The Effects of Sedimentation on the Water Quality of the Coralville Reservoir, Iowa

The Coralville Reservoir is a flood control impoundment located on the Iowa River just upstream from Iowa City. Since being placed in operation in 1958 its capacity at conservation pool level has been reduced nearly 20% by sedimentation. Studies of the reservoir\u27s fishery have been conducted since 1961. Fish population surveys do not indicate a noticeable modification of the fish population due to siltation. A decrease in the total fish population, primarily sport fish, occurring early in 1965, was due to oxygen depletion caused by heavy farm land runoff. Limnological studies of the Iowa River and the reservoir have been in progress since 1964. These indicate that gradual increases in plankton populations and threshold odor values have occurred in the reservoir and the river below the impoundment. Studies of the biological productivity of the reservoir indicate that maximum production frequently accompanies increased water level and inundation of littoral areas. Thus, increasing reservoir conservation pool level to compensate for loss of capacity due to sedimentation could contribute to water quality problems due to eutrophication

The Molecular Adsorbents Recycling System as a Liver Support System Based on Albumin Dialysis: A Summary of Preclinical Investigations, Prospective, Randomized, Controlled Clinical Trial, and Clinical Experience from 19 Centers

Artificial liver support aims to prolong survival time of patients with liver failure by detoxification. Albumin as a molecular adsorbent in dialysis solution is capable of attracting even tightly albumin-bound toxins from blood into the dialysate if a specific dialysis membrane is used and if the albumin's binding sites are on-line-purified by a sorbent/dialysis-based recycling system (i.e., molecular adsorbents recycling system, or MARS). The MARS technology has been shown to remove water-soluble and albumin-bound toxins and to provide renal support in case of renal failure. Fourteen centers have reported that MARS treatment improved mental status of patients with liver failure and hepatic encephalopathy. In treating liver failure and cholestasis, MARS was associated with hemodynamic stabilization, improvement of hepatic and kidney function, and disappearance of pruritus. In hepatic failure and hepatorenal syndrome, a prospective, randomized, controlled trial of MARS treatment was able to prolong survival time significantly. MARS has been used in 26 patients with acute liver failure or primary graft dysfunction. Nineteen centers reporting on 103 patients have shown that MARS treatment is safe, easy to handle, feasible, and effective.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73869/1/j.1525-1594.2002.06822.x.pd

X ray spectroscopy on the active ion in laser crystals

X-ray absorption and (resonant) emission spectroscopies combined measure the differences in crystal field parameters for the ground and core-excited states.</p

Ionization dynamics in expanding clusters studied by XUV pump probe spectroscopy

he expansion and disintegration dynamics of xenon clusters initiated by the ionization with femtosecond soft x ray extreme ultraviolet XUV pulses were studied with pump probe spectroscopy using the autocorrelator setup of the Free Electron LASer in Hamburg FLASH facility. The ionization by the first XUV pulse of 92 eV photon energy 8 1012 W cm amp; 8722;2 leads to the generation of a large number of quasi free electrons trapped by the space charge of the cluster ions. A temporally delayed, more intense probe 4 1013 W cm amp; 8722;2 pulse substantially increases a population of nanoplasma electrons providing a way of probing plasma states in the expanding cluster by tracing the average charge of fragment ions. The results of the study reveal a timescale for cluster expansion and disintegration, which depends essentially on the initial cluster size. The average charge state of fragment ions, and thus the cluster plasma changes significantly on a timescale of 1 3 p

Quantitative evaluation of transient valence orbital occupations in a 3d transition metal complex as seen from the metal and ligand perspective

It is demonstrated for the case of photo excited ferrocyanide how time resolved soft X ray absorption spectroscopy in transmission geometry at the ligand K edge and metal L3 edge provides quantitatively equivalent valence electronic structure information, where signatures of photo oxidation are assessed locally at the metal as well as the ligand. This allows for a direct and independent quantification of the number of photo oxidized molecules at two soft X ray absorption edges highlighting the sensitivity of X ray absorption spectroscopy to the valence orbital occupation of 3d transition metal complexes throughout the soft X ray rang

Phonon anharmonicities and ultrafast dynamics in epitaxial Sb2Te3

In this study we report on the investigation of epitaxially grown Sb2Te3 by employing Fourier-Transform transmission Spectroscopy (FTS) with laser-induced Coherent Synchrotron Radiation (CSR) in the Terahertz (THz) spectral range. Static spectra in the range between 20 and 120 cm−1 highlight a peculiar softening of an in-plane IR-active phonon mode upon temperature decrease, as opposed to all Raman active modes which instead show a hardening upon temperature decrease in the same energy range. The phonon mode softening is found to be accompanied by an increase of free carrier concentration. A strong coupling of the two systems (free carriers and phonons) is observed and further evidenced by exciting the same phonon mode at 62 cm−1 within an ultrafast pump-probe scheme employing a femtosecond laser as pump and a CSR single cycle THz pulse as probe. Separation of the free carrier contribution and the phonon resonance in the investigated THz range reveals that, both damping of the phonon mode and relaxation of hot carriers in the time domain happen on the same time scale of 5 ps. This relaxation is about a factor of 10 slower than expected from the Lorentz time-bandwidth limit. The results are discussed in the framework of phonon scattering at thermal and laser induced transient free carriers