Spectral slicing X-ray telescope with variable magnification

A telescope for viewing high frequency radiation (soft X-ray, extreme ultraviolet) is described. This telescope has a long focal length with a selection of magnifications despite a short housing. Light enters the telescope and is reflected by the telescope's primary optical system to one of several secondary mirrors at different locations on a movable frame. The secondary mirrors have varying degrees of magnification and select narrow spectral slices of the incident radiation. Thus, both the magnification and effective focal length field of view and wavelength can be altered by repositioning the moving frame. Configurations for spaceborne applications are discussed

Evidence linking coronal mass ejections with interplanetary magnetic clouds

Using proxy data for the occurrence of those mass ejections from the solar corona which are directed earthward, we investigate the association between the post-1970 interplanetary magnetic clouds of Klein and Burlaga and coronal mass ejections. The evidence linking magnetic clouds following shocks with coronal mass ejections is striking; six of nine clouds observed at Earth were preceded an appropriate time earlier by meter-wave type II radio bursts indicative of coronal shock waves and coronal mass ejections occurring near central meridian. During the selected periods when no clouds were detected near Earth, the only type II bursts reported were associated with solar activity near the limbs. Where the proxy solar data to be sought are not so clearly suggested, that is, for clouds preceding interaction regions and clouds within cold magnetic enhancements, the evidence linking the clouds and coronal mass ejections is not as clear; proxy data usually suggest many candidate mass-ejection events for each cloud. Overall, the data are consistent with and support the hypothesis suggested by Klein and Burlaga that magnetic clouds observed with spacecraft at 1 AU are manifestations of solar coronal mass ejection transients

The Extended Range X-Ray Telescope center director's discretionary fund report

An Extended Range X-Ray Telescope (ERXRT) of high sensitivity and spatial resolution capable of functioning over a broad region of the X-ray/XUV portion of the spectrum has been designed and analyzed. This system has been configured around the glancing-incidence Wolter Type I X-ray mirror system which was flown on the Skylab Apollo Telescope Mount as ATM Experiment S-056. Enhanced sensitivity over a vastly broader spectral range can be realized by the utilization of a thinned, back-illuminated, buried-channel Charge Coupled Device (CCD) as the X-ray/XUV detector rather than photographic film. However, to maintain the high spatial resolution inherent in the X-ray optics when a CCD of 30 micron pixel size is used, it is necessary to increase the telescope plate scale. This can be accomplished by use of a glancing-incidence X-ray microscope to enlarge and re-focus the primary image onto the focal surface of the CCD

Conditional quantum nonlocality in dimeric and trimeric arrays of organic molecules

Arrays of covalently bound organic molecules possess potential for light-harvesting and energy transfer applications due to the strong coherent dipole-dipole coupling between the transition dipole moments of the molecules involved. Here, we show that such molecular systems, based on perylene-molecules, can be considered as arrays of qubits that are amenable for laser-driven quantum coherent control. The perylene monomers exhibit dephasing times longer than four orders of magnitude a typical gating time, thus allowing for the execution of a large number of gate operations on the sub-picosecond timescale. Specifically, we demonstrate quantum logic gates and entanglement in bipartite (dimer) and tripartite (trimer) systems of perylene-based arrays. In dimers, naturally entangled states with a tailored degree of entanglement can be produced. The nonlocality of the molecular trimer entanglement is demonstrated by testing Mermin's (Bell-like) inequality violation.Comment: 14 pages, 8 figures, comments are welcom

Unusual Photophysical Properties of Porphyrin-Based Supramolecular Polymers Unveiled: The Role of Metal Ligands and Side Group Amide Connectivity

Supramolecular polymers based on porphyrins are an interesting model system, since the self-assembly and thus the photophysics can be modified by the chemical structure of the porphyrins, e.g., by a metal inserted in the ligand or by different (solubilizing) side groups. Here, we investigate the photophysical properties of supramolecular polymers based on free-base and Zn-centered porphyrins, each with different amide connectivity in the side chains, by absorption and (time-resolved) photoluminescence spectroscopy on solutions. We find that for all porphyrin derivatives the B-band absorption of supramolecular polymers is a superposition of H- and J-type aggregate spectra, while the Q-band absorption indicates only J-type aggregation. The emission of supramolecular polymers stems exclusively from the Q-band and shows only J-type behavior. For supramolecular polymers based on the free-base porphyrins, we identify only a single aggregate species, whereas for Zn-centered porphyrins, two distinct species coexist in solution, each with a (slightly) different arrangement of monomers. We rationalize this complex behavior by a slip-stacking of porphyrins along the direction of one of the two B-band transition dipole moments, resulting in simultaneous H- and J-type intermolecular coupling in the B-band. In the Q-band, with its transition dipole moments oriented 45° relative to the corresponding B-band moments, only J-type coupling is thus present. Our results demonstrate that the self-assembly and the photophysics of supramolecular polymers based on porphyrins can only be fully understood if spectral information from all bands is considered

Unusual Photophysical Properties of Porphyrin-Based Supramolecular Polymers Unveiled: The Role of Metal Ligands and Side Group Amide Connectivity

Supramolecular polymers based on porphyrins are an interesting model system, since the self-assembly and thus the photophysics can be modified by the chemical structure of the porphyrins, e.g., by a metal inserted in the ligand or by different (solubilizing) side groups. Here, we investigate the photophysical properties of supramolecular polymers based on free-base and Zn-centered porphyrins, each with different amide connectivity in the side chains, by absorption and (time-resolved) photoluminescence spectroscopy on solutions. We find that for all porphyrin derivatives the B-band absorption of supramolecular polymers is a superposition of H- and J-type aggregate spectra, while the Q-band absorption indicates only J-type aggregation. The emission of supramolecular polymers stems exclusively from the Q-band and shows only J-type behavior. For supramolecular polymers based on the free-base porphyrins, we identify only a single aggregate species, whereas for Zn-centered porphyrins, two distinct species coexist in solution, each with a (slightly) different arrangement of monomers. We rationalize this complex behavior by a slip-stacking of porphyrins along the direction of one of the two B-band transition dipole moments, resulting in simultaneous H- and J-type intermolecular coupling in the B-band. In the Q-band, with its transition dipole moments oriented 45° relative to the corresponding B-band moments, only J-type coupling is thus present. Our results demonstrate that the self-assembly and the photophysics of supramolecular polymers based on porphyrins can only be fully understood if spectral information from all bands is considered

Developing service promises accurate space weather forecasts in the future

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94931/1/eost10236.pd

Tests of Dynamical Flux Emergence as a Mechanism for CME Initiation

Current coronal mass ejection (CME) models set their lower boundary to be in the lower corona. They do not calculate accurately the transfer of free magnetic energy from the convection zone to the magnetically dominated corona because they model the effects of flux emergence using kinematic boundary conditions or simply assume the appearance of flux at these heights. We test the importance of including dynamical flux emergence in CME modeling by simulating, in 2.5D, the emergence of sub-surface flux tubes into different coronal magnetic field configurations. We investigate how much free magnetic energy, in the form of shear magnetic field, is transported from the convection zone to the corona, and whether dynamical flux emergence can drive CMEs. We find that multiple coronal flux ropes can be formed during flux emergence, and although they carry some shear field into the corona, the majority of shear field is confined to the lower atmosphere. Less than 10% of the magnetic energy in the corona is in the shear field, and this, combined with the fact that the coronal flux ropes bring up significant dense material, means that they do not erupt. Our results have significant implications for all CME models which rely on the transfer of free magnetic energy from the lower atmosphere into the corona but which do not explicitly model this transfer. Such studies of flux emergence and CMEs are timely, as we have new capabilities to observe this with Hinode and SDO, and therefore to test the models against observations

Enhancing Long-Range Energy Transport in Supramolecular Architectures by Tailoring Coherence Properties

Efficient long-range energy transport along supramolecular architectures of functional organic molecules is a key step in nature for converting sunlight into a useful form of energy. Understanding and manipulating these transport processes on a molecular and supramolecular scale is a long-standing goal. However, the realization of a well-defined system that allows for tuning morphology and electronic properties as well as for resolution of transport in space and time is challenging. Here we show how the excited-state energy landscape and thus the coherence characteristics of electronic excitations can be modified by the hierarchical level of H-type supramolecular architectures. We visualize, at room temperature, long-range incoherent transport of delocalized singlet excitons on pico- to nanosecond time scales in single supramolecular nanofibers and bundles of nanofibers. Increasing the degree of coherence, i.e., exciton delocalization, via supramolecular architectures enhances exciton diffusivities up to 1 order of magnitude. In particular, we find that single supramolecular nanofibers exhibit the highest diffusivities reported for H-aggregates so far

Deflection and Rotation of CMEs from Active Region 11158

Between the 13 and 16 of February 2011 a series of coronal mass ejections (CMEs) erupted from multiple polarity inversion lines within active region 11158. For seven of these CMEs we use the Graduated Cylindrical Shell (GCS) flux rope model to determine the CME trajectory using both Solar Terrestrial Relations Observatory (STEREO) extreme ultraviolet (EUV) and coronagraph images. We then use the Forecasting a CME's Altered Trajectory (ForeCAT) model for nonradial CME dynamics driven by magnetic forces, to simulate the deflection and rotation of the seven CMEs. We find good agreement between the ForeCAT results and the reconstructed CME positions and orientations. The CME deflections range in magnitude between 10 degrees and 30 degrees. All CMEs deflect to the north but we find variations in the direction of the longitudinal deflection. The rotations range between 5\mydeg and 50\mydeg with both clockwise and counterclockwise rotations occurring. Three of the CMEs begin with initial positions within 2 degrees of one another. These three CMEs all deflect primarily northward, with some minor eastward deflection, and rotate counterclockwise. Their final positions and orientations, however, respectively differ by 20 degrees and 30 degrees. This variation in deflection and rotation results from differences in the CME expansion and radial propagation close to the Sun, as well as the CME mass. Ultimately, only one of these seven CMEs yielded discernible in situ signatures near Earth, despite the active region facing near Earth throughout the eruptions. We suggest that the differences in the deflection and rotation of the CMEs can explain whether each CME impacted or missed the Earth.Comment: 18 pages, 6 figures, accepted in Solar Physic