TY  - JOUR
A1  - Tosi, Federico
A1  - Capaccioni, F.
A1  - Capria, M. T.
A1  - Mottola, Stefano
A1  - Zinzi, A.
A1  - Ciarniello, M.
A1  - Filacchione, G.
A1  - Hofstadter, M.
A1  - Fonti, S.
A1  - Formisano, M.
A1  - Kappel, David
A1  - Kührt, E.
A1  - Leyrat, C.
A1  - Vincent, J-B
A1  - Arnold, G.
A1  - De Sanctis, M. C.
A1  - Longobardo, Andrea
A1  - Palomba, E.
A1  - Raponi, A.
A1  - Rousseau, Batiste
A1  - Schmitt, Bernard
A1  - Barucci, Maria Antonietta
A1  - Bellucci, Giancarlo
A1  - Benkhoff, Johannes
A1  - Bockelee-Morvan, D.
A1  - Cerroni, P.
A1  - Combe, J-Ph
A1  - Despan, D.
A1  - Erard, Stéphane
A1  - Mancarella, F.
A1  - McCord, T. B.
A1  - Migliorini, Alessandra
A1  - Orofino, V
A1  - Piccioni, G.
T1  - The changing temperature of the nucleus of comet 67P induced by morphological and seasonal effects
JF  - Nature astronomy
N2  - Knowledge of the surface temperature distribution on a comet’s nucleus and its temporal evolution at different timescales is key to constraining its thermophysical properties and understanding the physical processes that take place at and below the surface. Here we report on time-resolved maps of comet 67P/Churyumov–Gerasimenko retrieved on the basis of infrared data acquired by the Visible InfraRed and Thermal Imaging Spectrometer (VIRTIS) onboard the Rosetta orbiter in 2014, over a roughly two-month period in the pre-perihelion phase at heliocentric distances between 3.62 and 3.31 au from the Sun. We find that at a spatial resolution ≤15 m per pixel, the measured temperatures point out the major effect that self-heating, due to the complex shape of the nucleus, has on the diurnal temperature variation. The bilobate nucleus of comet 67P also induces daytime shadowing effects, which result in large thermal gradients. Over longer periods, VIRTIS-derived temperature values reveal seasonal changes driven by decreasing heliocentric distance combined with an increasing abundance of ice within the uppermost centimetre-thick layer, which implies the possibility of having a largely pristine nucleus interior already in the shallow subsurface
Y1  - 2019
U6  - https://doi.org/10.1038/s41550-019-0740-0
SN  - 2397-3366
VL  - 3
IS  - 7
SP  - 649
EP  - 658
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Quirico, E.
A1  - Moroz, Liubov V.
A1  - Schmitt, B.
A1  - Arnold, Gabriele
A1  - Faure, M.
A1  - Beck, P.
A1  - Bonal, L.
A1  - Ciarniello, M.
A1  - Capaccioni, F.
A1  - Filacchione, G.
A1  - Erard, S.
A1  - Leyrat, C.
A1  - Bockelee-Morvan, D.
A1  - Zinzi, A.
A1  - Palomba, E.
A1  - Drossart, P.
A1  - Tosi, F.
A1  - Capria, M. T.
A1  - De Sanctis, M. C.
A1  - Raponi, A.
A1  - Fonti, S.
A1  - Mancarella, F.
A1  - Orofino, V.
A1  - Barucci, A.
A1  - Blecka, M. I.
A1  - Carlson, R.
A1  - Despan, D.
A1  - Faure, A.
A1  - Fornasier, S.
A1  - Gudipati, M. S.
A1  - Longobardo, A.
A1  - Markus, K.
A1  - Mennella, V.
A1  - Merlin, F.
A1  - Piccioni, G.
A1  - Rousseau, B.
A1  - Taylor, F.
T1  - Refractory and semi-volatile organics at the surface of comet 67P/Churyumov-Gerasimenko: Insights from the VIRTIS/Rosetta imaging spectrometer
JF  - Icarus : international journal of solar system studies
N2  - The VIRTIS (Visible, Infrared and Thermal Imaging Spectrometer) instrument aboard the Rosetta spacecraft has performed extensive spectral mapping of the surface of comet 67P/Churyumov-Gerasimenko in the range 0.3-5 mu m. The reflectance spectra collected across the surface display a low reflectance factor over the whole spectral range, two spectral slopes in the visible and near-infrared ranges and a broad absorption band centered at 3.2 mu m. The first two of these characteristics are typical of dark small bodies of the Solar System and are difficult to interpret in terms of composition. Moreover, solar wind irradiation may modify the structure and composition of surface materials and there is no unequivocal interpretation of these spectra devoid of vibrational bands. To circumvent these problems, we consider the composition of cometary grains analyzed in the laboratory to constrain the nature of the cometary materials and consider results on surface rejuvenation and solar wind processing provided by the OSIRIS and ROSINA instruments, respectively. Our results lead to five main conclusions: (i) The low albedo of comet 67P/CG is accounted for by a dark refractory polyaromatic carbonaceous component mixed with opaque minerals. VIRTIS data do not provide direct insights into the nature of these opaque minerals. However, according to the composition of cometary grains analyzed in the laboratory, we infer that they consist of Fe-Ni alloys and FeS sulfides. (ii) A semi-volatile component, consisting of a complex mix of low weight molecular species not volatilized at T similar to 220 K, is likely a major carrier of the 3.2 p.m band. Water ice contributes significantly to this feature in the neck region but not in other regions of the comet. COOH in carboxylic acids is the only chemical group that encompasses the broad width of this feature. It appears as a highly plausible candidate along with the NH4+ ion. (iii) Photolytic/thermal residues, produced in the laboratory from interstellar ice analogs, are potentially good spectral analogs. (iv) No hydrated minerals were identified and our data support the lack of genetic links with the CI, CR and CM primitive chondrites. This concerns in particular the Orgueil chondrite, previously suspected to have been of cometary origin. (v) The comparison between fresh and aged terrains revealed no effect of solar wind irradiation on the 3.2 mu m band. This is consistent with the presence of efficient resurfacing processes such as dust transport from the interior to the surface, as revealed by the OSIRIS camera. (C) 2016 Elsevier Inc. All rights reserved.
KW  - Comets
KW  - Organic chemistry
KW  - Infrared observations
KW  - Meteorites
KW  - Spectrophotometry
Y1  - 2016
U6  - https://doi.org/10.1016/j.icarus.2016.02.028
SN  - 0019-1035
SN  - 1090-2643
VL  - 272
SP  - 32
EP  - 47
PB  - Elsevier
CY  - San Diego
ER  - 
TY  - JOUR
A1  - Arhammar, C.
A1  - Pietzsch, Annette
A1  - Bock, Nicolas
A1  - Holmstroem, Erik
A1  - Araujo, C. Moyses
A1  - Grasjo, Johan
A1  - Zhao, Shuxi
A1  - Green, Sara
A1  - Peery, T.
A1  - Hennies, Franz
A1  - Amerioun, Shahrad
A1  - Föhlisch, Alexander
A1  - Schlappa, Justine
A1  - Schmitt, Thorsten
A1  - Strocov, Vladimir N.
A1  - Niklasson, Gunnar A.
A1  - Wallace, Duane C.
A1  - Rubensson, Jan-Erik
A1  - Johansson, Borje
A1  - Ahuja, Rajeev C.
T1  - Unveiling the complex electronic structure of amorphous metal oxides
JF  - Proceedings of the National Academy of Sciences of the United States of America
N2  - Amorphous materials represent a large and important emerging area of material's science. Amorphous oxides are key technological oxides in applications such as a gate dielectric in Complementary metal-oxide semiconductor devices and in Silicon-Oxide-Nitride-Oxide-Silicon and TANOS (TaN-Al2O3-Si3N4-SiO2-Silicon) flash memories. These technologies are required for the high packing density of today's integrated circuits. Therefore the investigation of defect states in these structures is crucial. In this work we present X-ray synchrotron measurements, with an energy resolution which is about 5-10 times higher than is attainable with standard spectrometers, of amorphous alumina. We demonstrate that our experimental results are in agreement with calculated spectra of amorphous alumina which we have generated by stochastic quenching. This first principles method, which we have recently developed, is found to be superior to molecular dynamics in simulating the rapid gas to solid transition that takes place as this material is deposited for thin film applications. We detect and analyze in detail states in the band gap that originate from oxygen pairs. Similar states were previously found in amorphous alumina by other spectroscopic methods and were assigned to oxygen vacancies claimed to act mutually as electron and hole traps. The oxygen pairs which we probe in this work act as hole traps only and will influence the information retention in electronic devices. In amorphous silica oxygen pairs have already been found, thus they may be a feature which is characteristic also of other amorphous metal oxides.
KW  - stochastic quench
KW  - X-ray absorption spectroscopy
KW  - ab initio
KW  - coating
Y1  - 2011
U6  - https://doi.org/10.1073/pnas.1019698108
SN  - 0027-8424
VL  - 108
IS  - 16
SP  - 6355
EP  - 6360
PB  - National Acad. of Sciences
CY  - Washington
ER  - 
TY  - JOUR
A1  - Sun, Y. -P.
A1  - Miao, Q.
A1  - Pietzsch, Annette
A1  - Hennies, F.
A1  - Schmitt, T.
A1  - Strocov, V. N.
A1  - Andersson, Joakim
A1  - Kennedy, B.
A1  - Schlappa, J.
A1  - Föhlisch, Alexander
A1  - Gel&rsquo, 
A1  - mukhanov, F.
A1  - Rubensson, J. -E.
T1  - Interference between Resonant and Nonresonant Inelastic X-Ray Scattering
JF  - PHYSICAL REVIEW LETTERS
N2  - A detailed study of inelastic x-ray scattering from the ground state to the (3)Sigma(g)(3 sigma(-1)(g)3s(g)(1)) state of the O-2 molecule is presented. The observed angular anisotropy shows that the vibrational excitations within this final state are strongly dependent on the polarization of the incident radiation. The analysis demonstrates that this is a manifestation of interference between resonant and direct nonresonant inelastic x-ray scattering. This interference provides a new tool to monitor nuclear dynamics by relative rotation of the polarization vectors of the incident and scattered photons.
Y1  - 2013
U6  - https://doi.org/10.1103/PhysRevLett.110.223001
SN  - 0031-9007
VL  - 110
IS  - 22
PB  - AMER PHYSICAL SOC
CY  - COLLEGE PK
ER  -