Nonsequential Double Recombination in Intense Laser Fields

A second plateau in the harmonic spectra of laser-driven two-electron atoms is observed both in the numerical solution of a low-dimensional model helium atom and using an extended strong field approximation. It is shown that the harmonics well beyond the usual cut-off are due to the simultaneous recombination of the two electrons, which were emitted during different, previous half-cycles. The new cut-off is explained in terms of classical trajectories. Classical predictions and the time-frequency analysis of the ab initio quantum results are in excellent agreement. The mechanism corresponds to the inverse single photon double ionization process in the presence of a (low frequency) laser field.Comment: 4 pages, RevTeX, v2 with an extended strong field approximation treatment of the process; instead, v1 describes an attosecond control scheme to enhance the proces

Silver-Zinc Battery Separator Material Development

Ethylene/acrylic acid separators for silver zinc battery application

Observation and modeling of energetic particles at synchronous orbit on July 29, 1977

In the twelve hours following a worldwide storm, there was a series of at least four magnetospheric substorms, the last and largest of which exhibited an expansion phase onset at approximately 1200 UT. Data from six spacecraft in three general local time groupings (0300, 0700, and 1300 LT) were examined and vector magnetic field data and energetic electron and ion data from approximately 15 keV to 2 MeV were employed

A Frequency Comb calibrated Solar Atlas

The solar spectrum is a primary reference for the study of physical processes in stars and their variation during activity cycles. In Nov 2010 an experiment with a prototype of a Laser Frequency Comb (LFC) calibration system was performed with the HARPS spectrograph of the 3.6m ESO telescope at La Silla during which high signal-to-noise spectra of the Moon were obtained. We exploit those Echelle spectra to study the optical integrated solar spectrum . The DAOSPEC program is used to measure solar line positions through gaussian fitting in an automatic way. We first apply the LFC solar spectrum to characterize the CCDs of the HARPS spectrograph. The comparison of the LFC and Th-Ar calibrated spectra reveals S-type distortions on each order along the whole spectral range with an amplitude of +/-40 m/s. This confirms the pattern found by Wilken et al. (2010) on a single order and extends the detection of the distortions to the whole analyzed region revealing that the precise shape varies with wavelength. A new data reduction is implemented to deal with CCD pixel inequalities to obtain a wavelength corrected solar spectrum. By using this spectrum we provide a new LFC calibrated solar atlas with 400 line positions in the range of 476-530, and 175 lines in the 534-585 nm range. The new LFC atlas improves the accuracy of individual lines by a significant factor reaching a mean value of about 10 m/s. The LFC--based solar line wavelengths are essentially free of major instrumental effects and provide a reference for absolute solar line positions. We suggest that future LFC observations could be used to trace small radial velocity changes of the whole solar photospheric spectrum in connection with the solar cycle and for direct comparison with the predicted line positions of 3D radiative hydrodynamical models of the solar photosphere.Comment: Accept on the 15th of October 2013. 9 pages, 10 figures. ON-lINE data A&A 201

Silver-Zinc Battery Separator Material Development

Ethylene/methyl acrylate copolymer synthesis for silver-zinc battery separator

Magnetospheric Response Times Following Southward IMF Turnings

We analyze the response times of various regions of the magnetosphere-ionosphere system to sudden southward turnings of the IMF. Our data set consists of 26 events during which the IMP BZ component was observed by WIND to change from a stea northward field to a southward field, which subsequently led to a substorm. The magnetospheric response to such IMF southward turnings is examined using data from the POLAR EFI experiment, the GOES 9 magnetometer, and ground magnetometers. The POLAR/EFI was used to investigate changes in the polar cap electric field which occurred in response to the changing interplanetary electric field, and these results are compared with response timings derived from high-latitude ground magnetometers. POLAR/EFI data show responses in the polar cap about 15 minutes after the arrival of the IMF change at the magnetopause. Auroral zone magnetograms and geosynchronous spacecraft measurements are utilized to evaluate the response timing within the closed field line region. In one event examined in detail, the start of a substorm growth phase was observed by GOES 9 in the midnight sector of geosynchronous orbit about two minutes before POLAR observed a response in the polar cap. Using superposed epoch analysis, we calculate typical response times in the polar cap, in the nightside plasma sheet, and in the ionosphere in order to discuss the various suggested mechanisms for information propagation from the subsolar magnetopause into the magnetosphere. We find that for the set of ten events for which the GOES 9 and the CANOPUS array are in the midnight sector, the field at geosynchronous as measured by GOES responds at or before the time of response in the polar cap as measured by POLAR, suggesting different methods of information propagation

MeV magnetosheath ions energized at the bow shock

A causal relationship between midlatitude magnetosheath energetic ions and bow shock magnetic geometry was previously established for ion energy up to 200 keV e−1 for the May 4, 1998, storm event. This study demonstrates that magnetosheath ions with energies above 200 keV up to 1 MeV simply extend the ion spectrum to form a power law tail. Results of cross-correlation analysis suggest that these ions also come directly from the quasi-parallel bow shock, not the magnetosphere. This is confirmed by a comparison of energetic ion fluxes simultaneously measured in the magnetosheath and at the quasi-parallel bow shock when both regions are likely connected by the magnetic field lines. We suggest that ions are accelerated at the quasi-parallel bow shock to energies as high as 1 MeV and subsequently transported into the magnetosheath during this event

A Laser Frequency Comb System for Absolute Calibration of the VTT Echelle Spectrograph

A wavelength calibration system based on a laser frequency comb (LFC) was developed in a co-operation between the Kiepenheuer-Institut f\"ur Sonnenphysik, Freiburg, Germany and the Max-Planck-Institut f\"ur Quantenoptik, Garching, Germany for permanent installation at the German Vacuum Tower Telescope (VTT) on Tenerife, Canary Islands. The system was installed successfully in October 2011. By simultaneously recording the spectra from the Sun and the LFC, for each exposure a calibration curve can be derived from the known frequencies of the comb modes that is suitable for absolute calibration at the meters per second level. We briefly summarize some topics in solar physics that benefit from absolute spectroscopy and point out the advantages of LFC compared to traditional calibration techniques. We also sketch the basic setup of the VTT calibration system and its integration with the existing echelle spectrograph.Comment: 9 pages, 2 figures; Solar Physics 277 (2012

Studies of the coordination behavior of substituted nitrogen donor ligands

This work is concerned with metal-complexes of extensively conjugated heterocyclic nitrogen donor ligands. Part I Four-coordinate complexes of zinc(II), cadmium(II), mercury(II) and palladium(II) of general formula MLLuPc₂ have been prepared with the ligands 4,4'-dicarboxyethyl-3,3',5,5' tetramethyldipyrromethene and 3,4'-dicarboxyethyl-5-chloro-3',4,5'-trimethyldipyrromethene. The complexes involve bidentate coordination of the dipyrromethene ligands. Those of the Group IIb metals are near regular tetrahedral while the palladium complex shown in this work to be square plansar. Complexes of palladium(II) of general formulae Pd₂Cl₂L₂ and PdX(L)(LH), where X is Cl⁻ and Br⁻ and L is either of the dipyrromethenes have also been prepared. Both types are square planar four-coordinate complexes, the first being chloro-bridged with two bidentate dipyrromethene ligands, and the second having one monodentate and one bidentate dipyrromethene ligand. The electronic absorption spectra of all the complexes have been measured and the observed bands have been assigned to intraligand π → π* transitions and to metal → ligand charge transfer transitions The proton magnetic resonance spectra of the complexes have been recorded and resonance peaks have been assigned to protons of particular groups substituted on the dipyrromethene ligands. The results of both these spectral studies are discussed with reference to the stereochemistry about the metal ion and the influence of ligand substituents on the metal-ligand bonding. The crystal and molecular structure of bis-(4,4'-dicarboxyethyl-3,3'-5,5'-tetramethyldipyrrometheneto-palladium(II) has been determined from a single crystal diffraction study. The compound is “stepped" square planar and the dipyrromethene ligands are found to deviate considerably from planarity. The structure of this compound is compared with those which have studied previously. The influences are found to similar compounds on stereochemistry of the metal ion (copper(II), nickel(II) and palladium(II)) and of bulky ligand substituents are discussed. Part II A number of o-phenanthroline complexes of iron(II) and ruthenium(II) have been prepared. These are all six-coordinate and have general formulae M(phen)₃²⁺ and M(phen)₂X₂ where X is Cl-, Br-, I-, SCN- and ON-, and phen is o-phenanthroline, 5-methyl-o-phenanthroline, 5-chloro-o-phenanthroline or 5-nitro-o-phenanthroline.. The electronic spectra of these complexes have been investigated in solution or in the solid state. Bands have been assigned to metal → ligand charge transfer transitions and intraligand π → π* transitions from comparisons with the results of earlier studies. Energies of the electronic transitions are discussed with reference to both the influence of the ligands and of the substituents on the phenanthroline ligand on the metal-ligand π-interactions