Soft x-ray free electron laser microfocus for exploring matter under extreme conditions

We have focused a beam (BL3) of FLASH (Free-electron LASer in Hamburg: lambda = 13.5 nm, pulse length 15 fs, pulse energy 10-40 mu J, 5Hz) using a fine polished off-axis parabola having a focal length of 270 mm and coated with a Mo/Si multilayer with an initial reflectivity of 67% at 13.5 nm. The OAP was mounted and aligned with a picomotor controlled six-axis gimbal. Beam imprints on poly(methyl methacrylate) -PMMA were used to measure focus and the focused beam was used to create isochoric heating of various slab targets. Results show the focal spot has a diameter of

Synthesis of the heterocyclic core of the alkaloids martinelline and martinellic acid

The tricyclic core of martinelline and martinellic acid was rapidly assembled utilising an imino Diels-Alder reaction of an imine derived from cinnamaldehyde with a cyclic enamide. The cycloaddition was completely regioselective though the exo endo selectivity was poor. These diastercoisomers were readily separated by flash chromatography and the relative stereochemistry of the exo-isomer confirmed by single crystal X-ray crystallography. This intermediate was converted to the central core of the aforementioned alkaloids in five additional synthetic operations. (C) 2001 Elsevier Science Ltd. All rights reserved.

Electronic Structure of an XUV Photogenerated Solid-Density Aluminum Plasma

By use of high intensity XUV radiation from the FLASH free-electron laser at DESY, we have created highly excited exotic states of matter in solid-density aluminum samples. The XUV intensity is sufficiently high to excite an inner-shell electron from a large fraction of the atoms in the focal region. We show that soft-x-ray emission spectroscopy measurements reveal the electronic temperature and density of this highly excited system immediately after the excitation pulse, with detailed calculations of the electronic structure, based on finite-temperature density functional theory, in good agreement with the experimental results.

Two-Photon Inner-Shell Ionization in the Extreme Ultraviolet

We have observed the simultaneous inner-shell absorption of two extreme-ultraviolet photons by a Xe atom in an experiment performed at the short-wavelength free electron laser facility FLASH. Photoelectron spectroscopy permitted us to unambiguously identify a feature resulting from the ionization of a single electron of the 4d subshell of Xe by two photons each of energy (93 +/- similar to 1) eV. The feature's intensity has a quadratic dependence on the pulse energy. The results are discussed and interpreted within the framework of recent results of ion spectroscopy experiments of Xe obtained at ultrahigh irradiance in the extreme-ultraviolet regime.

A Ring Rearrangement Approach to the Synthesis of Benzo[b]quinolizine and Benzoindolizine Architectures

An efficient ring rearrangement metathesis (RRM) approach to the synthesis of benzo[b]quinolizine and benzoindolizine systems from N-propargyl-phenanthridine derivatives is reported. A Hovel use of flash vacuum pyrolysis (FVP) for the Boc-deprotection of acid-sensitive substrates is also disclosed.

Non-intrusive tracking of commercial broiler chickens in situ at different stocking densities

Unlike several other farm animal species, the broiler chicken remains unprotected by species-specific legislation. The densities at which broilers should be kept is a highly contentious issue-some studies have demonstrated increased welfare problems at higher densities, whilst a few others have, contrary to expectations, suggested that broilers may actually find crowds of other birds attractive. A tracking method was developed and used to provide an insight into the social preferences of commercial broiler chickens in situ-inside commercial, closed-system broiler houses. The aim was to simultaneously assess the relative impact of global measures of density, such as target and actual stocking densities and local measures of the social environment on the behaviour and route taken to feed by focal birds. Birds were tracked inside 20 commercial broiler houses across the UK. Results from this study show that stocking density per se seems to have little direct effect on the individual behaviours of focal broiler chickens. However, there may still be an indirect effect of stocking density on broiler behaviour, mediated through the local social environment. (C) 2007 Elsevier B.V. All rights reserved.

Time-resolved resonance Raman scattering of triplet state anthracene in supercritical CO2

The first report of time-resolved resonance Raman (TR(3)) scattering in a supercritical fluid is presented. TR(3) spectra of the lowest triplet excited state (T-1) of anthracene in supercritical (SC) CO2 have been obtained over the pressure range 90-500 bar. These data have been complemented by conventional flash photolysis measurements of the excited state lifetime, transient absorbance difference, and fluorescence spectra over a similar pressure range. The spectroscopic data show systematic changes with increasing pressure; the Delta A spectra of the TI state recorded at two different temperatures display a red shift with increasing fluid pressure, which is in agreement with earlier work carried out over a smaller range of pressures. Similar shifts in the fluorescence are also observed. The vibrational frequencies of the T-1 state of anthracene are found to be relatively insensitive to applied pressure; indeed, the transient bands are readily identified by comparison with resonance Raman (RR) spectra of the T-1 state in cyclohexane solution. Small but well-defined shifts to lower cm(-1) with increasing pressure are observed in some of the vibrational bands of SC COE. The most marked change in the excited state Raman spectra is that the intensity of the T-1 anthracene features, relative to those of CO2, increases with applied pressure. The information which each of the above spectroscopic methods gives on the question of how pressure changes affect the structure and local environment of the excited state probe molecule in the SCF is discussed. Possible explanations for the observed increase in RR band intensities in terms of increased resonance Raman enhancement arising from the spectral shifts and/or the increased solubility of anthracene in CO2 with increasing pressure are also considered.

TRANSIENT RESONANCE RAMAN AND RAMAN SPECTROELECTROCHEMICAL STUDIES OF CUI COMPLEXES WITH POLYPYRIDYL LIGANDS

Studies by laser flash photolysis, transient Raman spectroscopy, and Raman and UV-vis spectroelectrochemistry are described in which the techniques have been used in parallel to compare the lowest energy charge-transfer excited states of Cu (1) complexes ([Cu(L)2]+ and [ (PPh3)2Cu(L)]+ [L = 2,2'-biquinoline (BIQ) or 6,7-dihydro-5,8-dimethyldibenzo[b,j] [1,10]-phenanthroline (DMCH)) with the species produced by electrochemical reduction in the same group of complexes. Transient resonance Raman spectra for the metal-to-ligand charge-transfer (MLCT) states of [Cu(DMCH)2]+ (1), [Cu(BIQ)2]+ (2), [Cu(DMCH)(PPh3)2]+ (3), and [Cu(BIQ)(PPh3)2]+ (4) are compared with the resonance Raman spectra of the same group of complexes following one-electron electrochemical reduction of the DMCH and BIQ ligands. The UV-vis and resonance Raman evidence suggests that the electrochemical reduction of the [Cu(I)L2]+ species proceeds according to the sequence [LCu(I)L]+ -->e- [LCu0L] -->e- [L.-Cu(I)L.-]-. Several features assignable to modes of the electrochemically generated DMCH.-and BIQ'- radical anions exhibit a close correspondence in both frequency and relative intensity with counterparts in the spectra of the MLCT states of 1 and 2. A notable exception is a band near 1590 cm-1 in the spectra of the electrochemically reduced species which occurs some 15 cm-1 lower in the corresponding spectra of the excited-state species. It is suggested that the shift may reflect the change in oxidation state of the metal center from Cu(I) to Cu(II) which occurs as a result of charge-transfer excitation.

Decay of Cystalline Order and Equilibration during the Solid-to-Plasma Transition Induced by 20-fs Microfocused 92-eV Free-Electron-Laser Pulses

We have studied a solid-to-plasma transition by irradiating Al foils with the FLASH free electron laser at intensities up to 10(16) W/cm(2). Intense XUV self-emission shows spectral features that are consistent with emission from regions of high density, which go beyond single inner-shell photoionization of solids. Characteristic features of intrashell transitions allowed us to identify Auger heating of the electrons in the conduction band occurring immediately after the absorption of the XUV laser energy as the dominant mechanism. A simple model of a multicharge state inverse Auger effect is proposed to explain the target emission when the conduction band at solid density becomes more atomiclike as energy is transferred from the electrons to the ions. This allows one to determine, independent of plasma simulations, the electron temperature and density just after the decay of crystalline order and to characterize the early time evolution.

KINETIC-STUDY OF PHOTOINDUCED ELECTRON-TRANSFER REACTIONS SENSITIZED BY COLLOIDAL CDS

The kinetics of the recovery of the photoinduced transient bleaching of colloidal CdS in the presence of different electron acceptors are examined. In the presence of the zwitterionic viologen, N,N'-dipropyl-2,2'-bipyridinium disulphonate, excitation of colloidal CdS at different flash intensities generates a series of decay profiles which are superimposed when normalized. The shape of the decay curves are as predicted by a first-order activation-controlled model for a log-normal distribution of particles sizes. In contrast, the variation in flash intensity in the presence of a second viologen, N,N'-dipropyl-4,4'-bipyridinium sulphonate, generates normalized decay traces which broaden with increasing flash intensity. This behaviour is predicted by a zero-order diffusion-controlled model for a log-normal distribution of particle radii. The photoreduction of a number of other oxidants sensitized by colloidal CdS is examined and the shape of the decay kinetics interpreted via either the first- or zero-order kinetics models. The rate constants and activation energies derived using these models are consistent with the values expected for an activation- or diffusion-controlled reaction.

The metamorphosis of supernova SN 2008D/XRF 080109: A link between supernovae and GRBs/hypernovae

The only supernovae (SNe) to show gamma-ray bursts ( GRBs) or early x-ray emission thus far are overenergetic, broad- lined type Ic SNe ( hypernovae, HNe). Recently, SN 2008D has shown several unusual features: (i) weak x-ray flash (XRF), (ii) an early, narrow optical peak, (iii) disappearance of the broad lines typical of SN Ic HNe, and (iv) development of helium lines as in SNe Ib. Detailed analysis shows that SN 2008D was not a normal supernova: Its explosion energy (E approximate to 6 x 10(51) erg) and ejected mass [similar to 7 times the mass of the Sun ( M.)] are intermediate between normal SNe Ibc and HNe. We conclude that SN 2008D was originally a similar to 30 M. star. When it collapsed, a black hole formed and a weak, mildly relativistic jet was produced, which caused the XRF. SN 2008D is probably among the weakest explosions that produce relativistic jets. Inner engine activity appears to be present whenever massive stars collapse to black holes.

Optical and infrared photometry of the Type IInSN1998S: days 11-146

We present contemporaneous optical and infrared (IR) photometric observations of the Type IIn SN 1998S covering the period between 11 and 146 d after discovery. The IR data constitute the first ever IR light curves of a Type IIn supernova. We use blackbody and spline fits to the photometry to examine the luminosity evolution. During the first 2-3 months, the luminosity is dominated by the release of shock-deposited energy in the ejecta. After similar to 100 d the luminosity is powered mostly by the deposition of radioactive decay energy from 0.15 +/-0.05 M-. of Ni-56 which was produced in the explosion. We also report the discovery of an astonishingly high IR excess, K-L'=2.5, that was present at day 130. We interpret this as being due to thermal emission from dust grains in the vicinity of the supernova. We argue that to produce such a high IR luminosity so soon after the explosion, the dust must be pre-existing and so is located in the circumstellar medium of the progenitor. The dust could be heated either by the UV/optical flash (IR echo) or by the X-rays from the interaction of the ejecta with the circumstellar material.

Crowd Control? Depictions of the Many in Anglo-Saxon Literature, with Particular Reference to the Old English Legend of the Seven Sleepers

This article argues for the distinctiveness of the presentation of crowds in the Old English version of the Legend of the Seven Sleepers . In traditional Old English poetry, crowds are mostly conspicuous by their absence, since the social groupings portrayed are typically those ofthe lord's retinue and the fellowship of the hall. In writings deriving from Latin traditions (in Anglo-Latin, Old English prose and strands of Old English poetry) such as historiography andhagiography, crowds are presented in highly conventional terms based on literary models. The crowd scenes in the Legend of the Seven Sleepers , on the other hand, have an immediacy and urgency that seem based on real-life experience of Anglo-Saxon England rather than simply imitative of the work's Latin (ultimately Greek) source or of other literary models. Drawing upon crowd theory and historical studies, the article demonstrates that the crowds in this text are presented in “domesticated” Anglo-Saxon terms and may be seen as reflective of growing urbanization in late Anglo-Saxon England. “Real” crowds are glimpsed elsewhere in Anglo-Saxon literature but in the Legend of the Seven Sleepers they are particularly foregrounded; this text also presents the literature's liveliest picture of town life more generally.