The population of deformed bands in 48^{48}Cr by emission of 8^{8}Be from the 32^{32}S + 24^{24}Mg reaction

Using particle-$\gamma$ coincidences we have studied the population of final states after the emission of 2 $\alpha$-particles and of $^{8}$Be in nuclei formed in $^{32}$S+$^{24}$Mg reactions at an energy of $\textrm{E}_{\rm L}(^{32}\textrm{S}) = 130 {\rm MeV}$. The data were obtained in a setup consisting of the GASP $\gamma$-ray detection array and the multidetector array ISIS. Particle identification is obtained from the $\Delta$E and E signals of the ISIS silicon detector telescopes, the $^{8}$Be being identified by the instantaneous pile up of the $\Delta$E and E pulses. $\gamma$-ray decays of the $^{48}$Cr nucleus are identified with coincidences set on 2 $\alpha$-particles and on $^{8}$Be. Some transitions of the side-band with $K^\pi=4^{-}$ show stronger population for $^{8}$Be emission relative to that of 2 $\alpha$-particles (by a factor $1.5-1.8$). This observation is interpreted as due to an enhanced emission of $^{8}$Be into a more deformed nucleus. Calculations based on the extended Hauser-Feshbach compound decay formalism confirm this observation quantitatively.Comment: 17 pages, 9 figures accepted for publication in J. Phys.

Rotating hyperdeformed quasi-molecular states formed in capture of light nuclei and in collision of very heavy ions

International audienceWithin a rotational liquid drop model including the nuclear proximity energy the l-dependent potential barriers governing the capture reactions of light nuclei and of very heavy ions have been determined. Rotating quasi-molecular hyperdeformed states appear at high angular momenta. The energy range of these very deformed high spin states is given for light systems. The same approach explains the observation of ternary cluster decay from56Ni and 60Zn through hyperdeformed shapes at angular momenta around 45 . The apparently observed superheavy nuclear systems in the U+Ni and U+Ge reactions at high excitation energy might correspond to these rotating isomeric states formed at very high angular momenta even though the shell effects vanish

Stray-light contamination and spatial deconvolution of slit-spectrograph observations

Stray light caused by scattering on optical surfaces and in the Earth's atmosphere degrades the spatial resolution of observations. We study the contribution of stray light to the two channels of POLIS. We test the performance of different methods of stray-light correction and spatial deconvolution to improve the spatial resolution post-facto. We model the stray light as having two components: a spectrally dispersed component and a component of parasitic light caused by scattering inside the spectrograph. We use several measurements to estimate the two contributions: observations with a (partly) blocked FOV, a convolution of the FTS spectral atlas, imaging in the pupil plane, umbral profiles, and spurious polarization signal in telluric lines. The measurements allow us to estimate the spatial PSF of POLIS and the main spectrograph of the German VTT. We use the PSF for a deconvolution of both spectropolarimetric data and investigate the effect on the spectra. The parasitic contribution can be directly and accurately determined for POLIS, amounting to about 5%. We estimate a lower limit of about 10% across the full FOV for the dispersed stray light. In quiet Sun regions, the stray-light level from the close surroundings (d< 2") of a given spatial point is about 20%. The stray light reduces to below 2% at a distance of 20" from a lit area for both POLIS and the main spectrograph. A two-component model of the stray-light contributions seems to be sufficient for a basic correction of observed spectra. The instrumental PSF obtained can be used to model the off-limb stray light, to determine the stray-light contamination accurately for observation targets with large spatial intensity gradients such as sunspots, and also allows one to improve the spatial resolution of observations post-facto.Comment: 14 pages, 16 figures, accepted by A&A. Version V2 revised for language editin

Two-dimensional solar spectropolarimetry with the KIS/IAA Visible Imaging Polarimeter

Spectropolarimetry at high spatial and spectral resolution is a basic tool to characterize the magnetic properties of the solar atmosphere. We introduce the KIS/IAA Visible Imaging Polarimeter (VIP), a new post-focus instrument that upgrades the TESOS spectrometer at the German VTT into a full vector polarimeter. VIP is a collaboration between the KIS and the IAA. We describe the optical setup of VIP, the data acquisition procedure, and the calibration of the spectropolarimetric measurements. We show examples of data taken between 2005 and 2008 to illustrate the potential of the instrument. VIP is capable of measuring the four Stokes profiles of spectral lines in the range from 420 to 700 nm with a spatial resolution better than 0.5". Lines can be sampled at 40 wavelength positions in 60 s, achieving a noise level of about 2 x 10E-3 with exposure times of 300 ms and pixel sizes of 0.17" x 0.17" (2 x 2 binning). The polarization modulation is stable over periods of a few days, ensuring high polarimetric accuracy. The excellent spectral resolution of TESOS allows the use of sophisticated data analysis techniques such as Stokes inversions. One of the first scientific results of VIP presented here is that the ribbon-like magnetic structures of the network are associated with a distinct pattern of net circular polarization away from disk center. VIP performs spectropolarimetric measurements of solar magnetic fields at a spatial resolution that is only slightly worse than that of the Hinode spectropolarimeter, while providing a 2D field field of view and the possibility to observe up to four spectral regions sequentially with high cadence. VIP can be used as a stand-alone instrument or in combination with other spectropolarimeters and imaging systems of the VTT for extended wavelength coverage.Comment: 10 pages, 8 figures, accepted by Astronomy and Astrophysics v2: figures updated with improved qualit

The social, cosmopolitanism and beyond

First, this article will outline the metaphysics of ‘the social’ that implicitly and explicitly connects the work of lassical and contemporary cosmopolitan sociologists as different as Durkheim, Weber, Beck and Luhmann. In a second step, I will show that the cosmopolitan outlook of classical sociology is driven by exclusive differences. In understanding human affairs, both classical sociology and contemporary cosmopolitan sociology reflect a very modernist outlook of epistemological, conceptual, methodological and disciplinary rigour that separates the cultural sphere from the natural objects of concern. I will suggest that classical sociology – in order to be cosmopolitan – is forced (1) to exclude non-social and non-human objects as part of its conceptual and methodological rigour, and (2) consequently and methodologically to rule out the non-social and the non-human. Cosmopolitan sociology imagines ‘the social’ as a global, universal explanatory device to conceive and describe the non-social and non-human. In a third and final step the article draws upon the work of the French sociologist Gabriel Tarde and offers a possible alternative to the modernist social and cultural other-logics of social sciences. It argues for a inclusive conception of ‘the social’ that gives the non-social and non-human a cosmopolitan voice as well

The energy of waves in the photosphere and lower chromosphere: III. Inversion setup for Ca II H spectra in local thermal equilibrium

The Ca II H line is one of the strongest lines in the solar spectrum and provides continuous information on the solar atmosphere from the photosphere to the lower chromosphere. We describe an inversion approach that reproduces observed Ca II H spectra assuming LTE. We developed an inversion strategy based on the SIR code. The approach uses a two-step procedure with an archive of pre-calculated spectra to fit the line core and a subsequent iterative modification to improve the fit in the line wing. Simultaneous spectra in the 630nm range can optionally be used to fix the continuum temperature. The method retrieves 1D temperature stratifications neglecting lateral radiative transport. LOS velocities are included by an empirical approach. An archive of about 300.000 pre-calculated spectra is more than sufficient to reproduce the line core of observed Ca II H spectra both in quiet Sun and in active regions. The final thermodynamical stratifications match observed and best-fit spectra to a level of about 0.5 (1) % of Ic in the line wing (core). Inversion schemes based on pre-calculated spectra allow one a reliable and relatively fast retrieval of solar properties from observed chromospheric spectra. The approach can be easily extended to an 1D NLTE case by a simple exchange of the pre-calculated archive spectra.Comment: 15 pages, 15 figures, accepted for publication in A&A. The animation will only be provided in the A&A online sectio

The energy of waves in the photosphere and lower chromosphere: IV. Inversion results of Ca II H spectra

Most static 1D atmosphere models in the quiet Sun predict a rise of the gas temperature at chromospheric layers, but numerical simulations only yield an increase in the brightness temperature. We investigate the thermal structure in the solar chromosphere as derived from an LTE inversion of Ca II H spectra in QS and active regions. We investigate the temperature stratifications on differences between magnetic and field-free regions in the QS, and between QS and ARs. We determine the energy content of individual calcium bright grains (BGs). The rms temperature fluctuations are below 100 K in the photosphere and 200-300 K in the chromosphere. The average temperature stratification in the QS does not exhibit a clear chromospheric temperature rise, opposite to the AR case. We find an energy content of about 7*10E18 J for BGs that repeat with a cadence of about 160 secs. The precursors of BGs have a vertical extent of about 200 km and a horizontal extent of about 1 Mm. The comparison of observed with synthetic NLTE profiles confirms that the solar chromosphere in the QS oscillates between an atmosphere in radiative equilibrium and one with a moderate chromospheric temperature rise. Two-dimensional x-z temperature maps exhibit nearly horizontal canopy-like structures with a few Mm extent around photospheric magnetic field concentrations at a height of about 600 km. The large difference between QS regions and ARs, and the better match of AR and non-LTE reference spectra suggest that magnetic heating processes are more important than commonly assumed. The temperature fluctuations in QS derived by the LTE inversion do not suffice on average to maintain a stationary chromospheric temperature rise. The spatially and vertically resolved information on the temperature structure allows one to investigate in detail the topology and evolution of the thermal structure in the lower solar atmosphere.Comment: 16 pages, 16 figures + 1 page Appendix, accepted by A&

From the stable to the exotic: clustering in light nuclei

A great deal of research work has been undertaken in alpha-clustering study since the pioneering discovery of 12C+12C molecular resonances half a century ago. Our knowledge on physics of nuclear molecules has increased considerably and nuclear clustering remains one of the most fruitful domains of nuclear physics, facing some of the greatest challenges and opportunities in the years ahead. The occurrence of "exotic" shapes in light N=Z alpha-like nuclei is investigated. Various approaches of the superdeformed and hyperdeformed bands associated with quasimolecular resonant structures are presented. Evolution of clustering from stability to the drip-lines is examined: clustering aspects are, in particular, discussed for light exotic nuclei with large neutron excess such as neutron-rich Oxygen isotopes with their complete spectroscopy.Comment: 15 pages, 5 figures, Presented at the International Symposium on "New Horizons in Fundamental Physics - From Neutrons Nuclei via Superheavy Elements and Supercritical Fields to Neutron Stars and Cosmic Rays" held at Makutsi Safari Farm, South Africa, December 23-29, 2015. arXiv admin note: substantial text overlap with arXiv:1402.6590, arXiv:1303.0960, arXiv:1408.0684, arXiv:1011.342

Binary reaction decays from 24Mg+12C

Charged particle and gamma decays in 24Mg* are investigated for excitation energies where quasimolecular resonances appear in 12C+12C collisions. Various theoretical predictions for the occurence of superdeformed and hyperdeformed bands associated with resonance structures with low spin are discussed within the measured 24Mg* excitation energy region. The inverse kinematics reaction 24Mg+12C is studied at E_lab(24Mg) = 130 MeV, an energy which enables the population of 24Mg states decaying into 12C+12C resonant break-up states. Exclusive data were collected with the Binary Reaction Spectrometer in coincidence with EUROBALL IV installed at the VIVITRON Tandem facility at Strasbourg. Specific structures with large deformation were selectively populated in binary reactions and their associated gamma decays studied. Coincident events associated with inelastic and alpha-transfer channels have been selected by choosing the excitation energy or the entry point via the two-body Q-values. The analysis of the binary reaction channels is presented with a particular emphasis on 24Mg-gamma, 20Ne-gamma and 16O-gamma coincidences. New information (spin and branching ratios) is deduced on high-energy states in 24Mg and 16O, respectively.Comment: 27 pages, 8 figures, 1 tabl