On the recombination in high-order harmonic generation in molecules

We show that the dependence of high-order harmonic generation (HHG) on the molecular orientation can be understood within a theoretical treatment that does not involve the strong field of the laser. The results for H_2 show excellent agreement with time-dependent strong field calculations for model molecules, and this motivates a prediction for the orientation dependence of HHG from the N_2 3s_g valence orbital. For both molecules, we find that the polarization of recombination photons is influenced by the molecular orientation. The variations are particularly pronounced for the N_2 valence orbital, which can be explained by the presence of atomic p-orbitals.Comment: 6 pages 7 figure

Interpretation Of The Space Bandwidth Product As The Entropy Of Distinctconnection Patterns In Multifacet Optical Interconnection Architectures

Cataloged from PDF version of article.We show that the entropy of the distinct connection patterns that are possible with multifacet optical interconnection architectures is approximately equal to the space-bandwidth product of the optical system

Investigation of a direction sensitive sapphire detector stack at the 5 GeV electron beam at DESY-II

Extremely radiation hard sensors are needed in particle physics experiments to instrument the region near the beam pipe. Examples are beam halo and beam loss monitors at the Large Hadron Collider, FLASH or XFEL. Currently artificial diamond sensors are widely used. In this paper single crystal sapphire sensors are considered as a promising alternative. Industrially grown sapphire wafers are available in large sizes, are of low cost and, like diamond sensors, can be operated without cooling. Here we present results of an irradiation study done with sapphire sensors in a high intensity low energy electron beam. Then, a multichannel direction-sensitive sapphire detector stack is described. It comprises 8 sapphire plates of 1 cm^2 size and 525 micro m thickness, metallized on both sides, and apposed to form a stack. Each second metal layer is supplied with a bias voltage, and the layers in between are connected to charge-sensitive preamplifiers. The performance of the detector was studied in a 5 GeV electron beam. The charge collection efficiency measured as a function of the bias voltage rises with the voltage, reaching about 10 % at 950 V. The signal size obtained from electrons crossing the stack at this voltage is about 22000 e, where e is the unit charge. The signal size is measured as a function of the hit position, showing variations of up to 20 % in the direction perpendicular to the beam and to the electric field. The measurement of the signal size as a function of the coordinate parallel to the electric field confirms the prediction that mainly electrons contribute to the signal. Also evidence for the presence of a polarisation field was observed.Comment: 13 pages, 7 figures, 3 table

Spin polarization of the Ar* 2p−11/2 4s and 2p−11/2 3d resonant Auger decay

The spin-resolved Auger decay of the Ar 2p−11/2 3d state was measured at moderate energy resolution and compared with the decay of the 2p−11/2 4s. The former shows a lower transferred spin polarization and a similar, if not higher, dynamical spin polarization, supporting the statement that a fully resolved spectrum is not a necessary condition for observing dynamical spin polarization. An interpretation of the spin polarization as configuration interaction induced effect in the final ionic state leads to partial agreement with our relativistic distorted wave calculation utilizing a 36 configuration state function basis set. Comparison of the experimental and numerical results leads to ambiguities for at least one Auger line. A hypothetical, qualitative interpretation is discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/58121/2/b7_17_012.pd

Fourier transforming a trapped Bose-Einstein condensate by waiting a quarter of the trap period: simulation and applications

We investigate the property of isotropic harmonic traps to Fourier transform a weakly interacting Bose–Einstein condensate (BEC) every quarter of a trap period. We solve the Gross–Pitaevskii equation numerically to investigate the time evolution of interacting BECs in the context of the Fourier transform, and we suggest potential applications

A multi-decadal meridional displacement of the Subpolar Front in the Newfoundland Basin

Observations since the 1950s show a multi-decadal cycle of a meridional displacement of the Subpolar Front (SPF) in the Newfoundland Basin (NFB) in the North Atlantic. The SPF displacement is associated with corresponding variations in the path of the North Atlantic Current. We use the ocean general circulation model MPIOM with enhanced horizontal and vertical resolutions and forced with NCEP/NCAR reanalysis data to study the relation of the SPF displacement to atmospheric forcing, intensities of the subpolar gyre (SPG) and Meridional Overturning Circulation (MOC), and Labrador Sea Water (LSW) volume. The simulations indicate that the SPF displacement is associated with a circulation anomaly between the SPG and the subtropical gyre (STG), an inter-gyre gyre with a multi-decadal time scale. A sensitivity experiment indicates that both wind stress curl (WSC) and heat fluxes (which match LSW changes) contribute to the circulation anomalies in the frontal region and to the SPF displacement. An anticyclonic inter-gyre gyre is related to negative WSC and LSW anomalies and to a SPF north of its climatological position, indicating an expanding STG. A cyclonic inter-gyre gyre is related to positive WSC and LSW anomalies and a SPF south of its climatological position, indicating an expanding SPG. Therefore, the mean latitudinal position of the SPF in the NFB (a "SPF index") could be an indicator of the amount of LSW in the inter-gyre region. Spreading of LSW anomalies intensifies the MOC, suggesting our SPF index as predictor of the MOC intensity at multi-decadal time scales. The meridional displacement of the SPF has a pronounced influence on the meridional heat transport, both on its gyre and overturning components.<br

Evolution of Global Ocean Tide Levels Since the Last Glacial Maximum

This study addresses the evolution of global tidal dynamics since the Last Glacial Maximum focusing on the extraction of tidal levels that are vital for the interpretation of geologic sea-level markers. For this purpose, we employ a truly-global barotropic ocean tide model which considers the non-local effect of Self-Attraction and Loading. A comparison to a global tide gauge data set for modern conditions yields agreement levels of 65%–70%. As the chosen model is data-unconstrained, and the considered dissipation mechanisms are well understood, it does not have to be re-tuned for altered paleoceanographic conditions. In agreement with prior studies, we find that changes in bathymetry during glaciation and deglaciation do exert critical control over the modeling results with minor impact by ocean stratification and sea ice friction. Simulations of 4 major partial tides are repeated in time steps of 0.5–1 ka and augmented by 4 additional partial tides estimated via linear admittance. These are then used to derive time series from which the tidal levels are determined and provided as a global data set conforming to the HOLSEA format. The modeling results indicate a strengthened tidal resonance by M2, but also by O1, under glacial conditions, in accordance with prior studies. Especially, a number of prominent changes in local resonance conditions are identified, that impact the tidal levels up to several meters difference. Among other regions, resonant features are predicted for the North Atlantic, the South China Sea, and the Arctic Ocean

Fractional Fourier Transform- Simulations and experimental results

Cataloged from PDF version of article.Recently two optical interpretations of the fractional Fourier transform operator were introduced. We address implementation issues of the fractional-Fourier-transform operation. We show that the original bulk-optics configuration for performing the fractional-Fourier-transform operation 3J. Opt. Soc. Am. A 10, 2181 1199324 provides a scaled output using a fixed lens. For obtaining a non-scaled output, an asymmetrical setup is suggested and tested. For comparison, computer simulations were performed. A good agreement between computer simulations and experimental results was obtained

Orbital order in the low-dimensional quantum spin system TiOCl probed by ESR

We present electron spin resonance data of Ti$^{3+}$ (3$d^1$) ions in single crystals of the novel layered quantum spin magnet TiOCl. The analysis of the g tensor yields direct evidence that the d_{xy} orbital from the t_{2g} set is predominantly occupied and owing to the occurrence of orbital order a linear spin chain forms along the crystallographic b axis. This result corroborates recent theoretical LDA+U calculations of the band structure. The temperature dependence of the parameters of the resonance signal suggests a strong coupling between spin and lattice degrees of freedom and gives evidence for a transition to a nonmagnetic ground state at 67 K.Comment: revised version, accepted for publication in Phys. Rev. B, Rapid Com