H. Rothard
University of Caen Lower Normandy
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European Physical Journal A | 1990
J. Bartke; H. Bialkowska; R. Bock; R. Brockmann; S. I. Chase; I. Derado; V. Eckardt; J. Eschke; C. Favuzzi; D. Ferenc; B. Fleischmann; M. Fuchs; M. Gazdzicki; H.J. Gebauer; E. Gladysz; C. Guerra; O. Hansen; John William Harris; W. Heck; T. J. Humanic; K. Kadija; S. Kabana; A. Karabarbounis; K. Keidel; J. Kosiec; M. Kowalski; A. Kühmichel; M. Lahanas; J.Y. Lee; M. J. LeVine
AbstractThe production of Λ,
Astronomy and Astrophysics | 2009
E. Seperuelo Duarte; P. Boduch; H. Rothard; T. Been; E. Dartois; L. S. Farenzena; E.F. da Silveira
Astronomy and Astrophysics | 2010
E. Seperuelo Duarte; A. Domaracka; P. Boduch; H. Rothard; E. Dartois; E.F. da Silveira
\bar \Lambda
Astronomy and Astrophysics | 2011
A. L. F. de Barros; V. Bordalo; E. Seperuelo Duarte; E.F. da Silveira; A. Domaracka; H. Rothard; P. Boduch
Astronomy and Astrophysics | 2013
E. Dartois; J. J. Ding; A. L. F. de Barros; P. Boduch; R. Brunetto; M. Chabot; A. Domaracka; M. Godard; X. Y. Lv; C. F. Mejía Guamán; T. Pino; H. Rothard; E.F. da Silveira; J.C. Thomas
andKs0 has been studied in 200 GeV/nucleonp+S and S+S collisions in the streamer chamber of the NA35 experiment at the CERN SPS. Significant enhancement of the multiplicities of all observed strange particles relative to negative hadrons was observed in central S+S collisions, as compared top+p andp+S collisions. The latter collisions show no overall (relative) strangeness enhancement overp+p, but the rapidity distributions and hadron multiplicities indicate some secondary cascading production of Λ particles in thep+S andp+Au collisions. The Λ polarization in central S+S collisions was found to be compatible with zero up topT=2 GeV/c.
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms | 1996
A. Billebaud; D. Dauvergne; M. Fallavier; R. Kirsch; Jean-Philippe Poizat; J. Remillieux; H. Rothard; Jean-Paul Thomas
Context : Ices present in different astrophysical environments are exposed to ion irradiation from cosmic rays (H to heavier than Fe) in the keV to GeV energy range. Aims : The objective of this work is to study the effects produced in astrophysical ices by heavy ions at relatively high energies (MeV) in the electronic energy loss regime and compare them with those produced by protons. Methods : C18O2 was condensed on a CsI substrate at 13 K and it was irradiated by 46 MeV 58Ni11+ up to a final fluence of 1.5 × 1013 cm−2 at a flux of 2 × 109 cm−2 s−1. The ice was analyzed in situ by infrared spectroscopy (FTIR) in the 5000−600 cm−1 range. Results : The CO2 destruction was observed, as well as the formation of other species such as CO, CO3, O3, and C3. The destruction cross section of CO2 is found to be 1.7×10−13 cm2, while those for the formation of CO, CO3, and O3 molecules are 1.6 × 10−13 cm2, 4.5 × 10−14 cm2, and 1.5 × 10−14 cm2, respectively. The sputtering yield of the CO2 ice is 4.0 × 104 molecules/impact, four orders of magnitude higher than for H projectiles at the same velocity. This allows us to estimate the contribution of the sputtering by heavy ions as compared to protons in the solar winds and in cosmic rays. Conclusions : The present results show that heavy ions play an important role in the sputtering of astrophysical ices. Furthermore, this work confirms the quadratic stopping power dependence of sputtering yields.
European Physical Journal C | 1994
T. Alber; H. Appelshäuser; J. Bächler; J. Bartke; H. Bialkowska; M. A. Bloomer; R. Bock; W.J. Braithwaite; D. Brinkmann; R. Brockmann; P. Buncic; P. Chan; S.I. Chase; J. G. Cramer; P.B. Cramer; I. Derado; V. Eckardt; J. Eschke; C. Favuzzi; D. Ferenc; B. Fleischmann; P. Foka; M. Fuchs; M. Gaździcki; E. Gladysz; J. Gunther; John William Harris; M. Hoffmann; P. Jacobs; S. Kabana
Context. Within dense interstellar clouds, from their periphery to regions deep inside, ice mantles on dust grains are exposed to cosmic-ray irradiation. Various swift ions contribute from protons to iron in the keV to TeV energy range. Observations show that in some lines of sight condensed CO molecules are an important component of the ice. Aims. We irradiate CO ices with Ni ions of relatively high energy (50 and 537 MeV) to simulate the effects produced by fast heavy cosmic-ray ions in interstellar grain mantles. Methods. CO gas is condensed on a CsI substrate at 13 K and irradiated by 50 MeV 58Ni13+ and 537 MeV 64Ni24+ ions up to a final fluence of ≈1 × 1013 cm−2, at a flux of 1 × 109 cm−2 s−1. The sputtering yields, the destruction rate of CO, and the rate of formation of new molecular species are measured in situ by Fourier transform infrared spectroscopy (FTIR). Results. The measured CO destruction cross-sections and sputtering yields induced by Ni ions are, respectively, (i) for 50 MeV, σd = 1.0×10−13 cm2 and Y = 7×104 molecules/impact; (ii) for 537 MeV, σd = 3.0×10−14 cm2 and Y = 5.85×104 molecules/impact. Based on the present and previous results, the desorption rates induced by H, Ni, and Fe ions are estimated for a wide range of energies. The contribution of the heavy ions is found to dominate over that of protons in the interstellar medium.
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms | 1988
K. Kroneberger; A. Clouvas; G. Schlüssler; P. Koschar; J. Kemmler; H. Rothard; C. Biedermann; O. Heil; M. Burkhard; K.O. Groeneveld
Laboratory data of CH4 ice radiolysis promoted by fast heavy ions are obtained by infrared spectroscopy (FTIR). CH4 molecules are condensed on a CsI substrate at 15 K, and the ice layer is bombarded by 220 MeV 16 O 7+ ion beam. The ice thickness is thin enough to be traversed by projectiles at constant velocity close to the equilibrium charge state. The induced CH4 dissociation gives rise to the formation of molecular species CH3 ,C 2H2 ,C 2H4 ,C 2H6 ,a nd C 3H8. Their formation and dissociation cross sections are determined. C2H6 represent the most abundant daughter molecules. The carbon budget analysis of CH4 and its radiolysis products shows that the column density of carbon atoms contained in the methane destroyed during ion irradiation is 30−50% greater than the sum for the column densities of the newly formed species. As an astrophysical implication, the current results allow estimation of chemical reaction rates in ices covering interstellar grains.
Astronomy and Astrophysics | 2015
E. Dartois; B. Augé; P. Boduch; R. Brunetto; M. Chabot; A. Domaracka; J. J. Ding; O. Kamalou; X. Y. Lv; H. Rothard; E.F. da Silveira; J.C. Thomas
Context. Cosmic ray ion irradiation affects the chemical composition of and triggers physical changes in interstellar ice mantles in space. One of the primary structural changes induced is the loss of porosity, and the mantles evolve toward a more compact amorphous state. Previously, ice compaction was monitored at low to moderate ion energies. The existence of a compaction threshold in stopping power has been suggested.Aims. In this article we experimentally study the effect of heavy ion irradiation at energies closer to true cosmic rays. This minimises extrapolation and allows a regime where electronic interaction always dominates to be explored, providing the ice compaction cross section over a wide range of electronic stopping power.Methods. High-energy ion irradiations provided by the GANIL accelerator, from the MeV up to the GeV range, are combined with in-situ infrared spectroscopy monitoring of ice mantles. We follow the IR spectral evolution of the ice as a function of increasing fluence (induced compaction of the initial microporous amorphous ice into a more compact amorphous phase). We use the number of OH dangling bonds of the water molecule, i.e. pending OH bonds not engaged in a hydrogen bond in the initially porous ice structure as a probe of the phase transition. These high-energy experiments are combined with lower energy experiments using light ions (H, He) from other facilities in Catania, Italy, and Washington, USA.Results. We evaluated the cross section for the disappearance of OH dangling bonds as a function of electronic stopping power. A cross-section law in a large energy range that includes data from different ice deposition setups is established. The relevant phase structuring time scale for the ice network is compared to interstellar chemical time scales using an astrophysical model.Conclusions. The presence of a threshold in compaction at low stopping power suggested in some previous works seems not to be confirmed for the high-energy cosmic rays encountered in interstellar space. Ice mantle porosity or pending bonds monitored by the OH dangling bonds is removed efficiently by cosmic rays. As a consequence, this considerably reduces the specific surface area available for surface chemical reactions.
Nuclear Physics | 1995
M. Gaździcki; T. Alber; H. Appelshäuser; J. Bächler; J. Bartke; H. Bialkowska; M. A. Bloomer; R. Bock; W.J. Braithwaite; D. Brinkmann; R. Brockmann; P. Buncic; P. Chan; J. G. Cramer; P.B. Cramer; I. Derado; V. Eckardt; J. Eschke; C. Favuzzi; D. Ferenc; B. Fleischmann; P. Foka; M. Fuchs; E. Gladysz; J. Gunther; John William Harris; M. Hoffmann; P. Jacobs; S. Kabana; K. Kadija
Abstract The yields of backward and forward electrons resulting from Hn+ cluster (n=1–13) interactions with carbon foils in the 40–120 keV/proton energy range have been measured as a function of the cluster size and of the foil thickness. A strong reduction of both backward and forward yields per proton is observed in comparison to free proton yields, with a saturation for n ⋍ 9 . Surprisingly the forward cluster effect persists for foils as thick as 3000 A.