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804 results on '"Descouvemont, P."'

102. Improved astrophysical rate for the 18O(p,α)15N reaction by underground measurements

Author

Bruno, C.G., Aliotta, M., Descouvemont, P., Best, A., Davinson, T., Bemmerer, D., Boeltzig, A., Broggini, C., Caciolli, A., Cavanna, F., Chillery, T., Ciani, G.F., Corvisiero, P., Depalo, R., Di Leva, A., Elekes, Z., Ferraro, F., Formicola, A., Fülöp, Zs., Gervino, G., Guglielmetti, A., Gustavino, C., Gyürky, Gy., Imbriani, G., Junker, M., Lugaro, M., Marigo, P., Menegazzo, R., Mossa, V., Pantaleo, F.R., Piatti, D., Prati, P., Stöckel, K., Straniero, O., Strieder, F., Szücs, T., Takács, M.P., and Trezzi, D.

Published
2019
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105. Recent results of the 14N(p, γ) 15O measurement at LUNA

Author

Costantini, H., Angulo, C., Bemmerer, D., Bonetti, R., Broggini, C., Confortola, F., Corvisiero, P., Cruz, J., Descouvemont, P., Formicola, A., Fülop, Z., Gervino, G., Guglielmetti, A., Gustavino, C., Gyürky, G., Imbriani, G., Jesus, A.P., Junker, M., Lemut, A., Menegazzo, R., Prati, P., Roca, V., Rolfs, C., Romano, M., Rossi Alvarez, C., Schümann, F., Somorjai, E., Straniero, O., Strieder, F., Terrasi, F., Trautvetter, H.P., Vomiero, A., and Zavatarelli, S.

Published
2005
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109. Improved astrophysical rate for the O(p, ) N reaction by underground measurements

Author

Bruno, C.G., Aliotta, M., Descouvemont, P., Best, A., Davinson, T., Bemmerer, D., Boeltzig, A., Broggini, C., Caciolli, A., Cavanna, F., Chillery, T., Ciani, G.F., Corvisiero, P., Depalo, R., Di Leva, A., Elekes, Z., Ferraro, F., Formicola, A., Fülöp, Zs., Gervino, G., Guglielmetti, A., Gustavino, C., Gyürky, Gy., Imbriani, G., Junker, M., Lugaro, M., Marigo, P., Menegazzo, R., Mossa, V., Pantaleo, F.R., Piatti, D., Prati, P., Stöckel, K., Straniero, O., Strieder, F., Szücs, T., Takács, M.P., and Trezzi, D.

Abstract

The $^{18}$O(p,α)$^{15}$N reaction affects the synthesis of $^{15}$N, $^{18}$O and $^{19}$F isotopes, whose abundances can be used to probe the nucleosynthesis and mixing processes occurring deep inside asymptotic giant branch (AGB) stars. We performed a low-background direct measurement of the $^{18}$O(p,α)$^{15}$N reaction cross-section at the Laboratory for Underground Nuclear Astrophysics (LUNA) from center of mass energy Ec.m.=340 keV down to Ec.m.=55 keV, the lowest energy measured to date corresponding to a cross-section of less than 1 picobarn/sr. The strength of a key resonance at center of mass energy Er=90 keV was found to be a factor of 10 higher than previously reported. A multi-channel R-matrix analysis of our and other data available in the literature was performed. Over a wide temperature range, T=0.01–1.00 GK, our new astrophysical rate is both more accurate and precise than recent evaluations. Stronger constraints can now be placed on the physical processes controlling nucleosynthesis in AGB stars with interesting consequences on the abundance of $^{18}$O in these stars and in stardust grains, specifically on the production sites of oxygen-rich Group II grains.

Published
2019

110. Spectroscopy of high lying resonances in 9Be produced with radioactive 8Li beams

Author

Lépine-Szily A., Leistenschneider E., Mendes D. R., Descouvemont P., Lichtenthäler R., Guimarães V., de Faria P. N., Barioni A., Pires K. C. C., Morcelle V., Pampa Condori R., Moraes M. C., Scarduelli V., Rossi E., Zagatto V. A., Santos H., Aguiar V. A. P., Britos T., Assunção M., Zamora J. C., Duarte J., and Shorto J. M. B.

Subjects
Physics, QC1-999
Abstract

We present the results of the 8Li(p,α)5He and 8Li(p,p)8Li reactions measured at the RIBRAS (Radioactive Ion Beams in Brazil) system. The experiment was realized in inverse kinematics using a thick [CH2]n polyethylene target and an incident 8Li beam, produced by RIBRAS. Using the thick target method, the complete excitation function could be measured between Ecm = 0.2 − 2.1 MeV, which includes the Gamow peak energy region. The excitation function of the 8Li(p,α)5He reaction, populating resonances between 16.888 and 19.0 MeV in 9Be, was obtained[1] and the resonances were fitted using R-matrix calculations. This study shed light on spins, parities, partial widths and isospin values of high lying resonances in 9Be. The measurement of the resonant elastic scattering 8Li(p,p)8Li populating resonances in the same energy region can constrain the resonance parameters. Preliminary results of the elastic scattering are also presented.

Published
2014
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111. Role of the Hoyle state in the 12C+12C fusion at low energies

Author

Descouvemont P. and Assunção M.

Subjects
Physics, QC1-999
Abstract

The 12C+12C fusion reaction is investigated in a multichannel folding model, using the density-dependent DDM3Y nucleon-nucleon interaction. The 12C(01+, 2+, 02+, 3−) states are included, and their densities are taken from a microscopic cluster calculation. Absorption to fusion channels is simulated by a short-range imaginary potential and the model does not contain any fitting parameter. We compute elastic and fusion cross sections simultaneously. The role of 12C+12C inelastic channels and, in particular, of the 12C(01+)+12C(02+) channel involving the Hoyle state is important even at low energies.

Published
2014
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117. Erratum: The Li8(p,α)He5 reaction at low energies, and Be9 spectroscopy around the proton threshold [Phys. Rev. C 86 , 064321 (2012)]

Author

Mendes, D. R., primary, Lépine-Szily, A., additional, Descouvemont, P., additional, Lichtenthäler, R., additional, Guimarães, V., additional, de Faria, P. N., additional, Barioni, A., additional, Pires, K. C. C., additional, Morcelle, V., additional, Pampa Condori, R., additional, Morais, M. C., additional, Leistenschneider, E., additional, Lima, C. E. F., additional, Zamora, J. C., additional, Alcantara, J. A., additional, Zagatto, V., additional, Assunção, M., additional, and Shorto, J. M. B., additional

Published
2018
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127. Resonances in 12C and 24Mg: what do we learn from a microscopic cluster theory?

Author

Descouvemont, P.

Abstract

We discuss resonance properties in three-body systems, with examples on 12 C and 24 Mg . We use a microscopic cluster model, where the generator coordinate is defined in the hyperspherical formalism. The 12 C nucleus is described by an α + α + α structure, whereas 24 Mg is considered as an 16 O + α + α system. We essentially pay attention to resonances. We review various techniques which may extend variational methods to resonances. We consider 0 + and 2 + states in 12 C and 24 Mg . We show that the r.m.s. radius of a resonance is strongly sensitive to the variational basis. This has consequences for the Hoyle state ( 0 2 + state in 12 C ) whose radius has been calculated or measured in several works. In 24 Mg , we identify two 0 + resonances slightly below the three-body threshold. [ABSTRACT FROM AUTHOR]

Published
2021
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128. Constraints on the variations of fundamental couplings by stellar models

Author

Coc, A., Sylvia Ekström, Descouvemont, P., Meynet, G., Olive, K. A., Uzan, J. -Ph, Vangioni, E., CSNSM AN, Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse (CSNSM), Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11)-Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Physique Nucléaire Théorique et Physique Mathématique, Université libre de Bruxelles (ULB), Institut d'Astrophysique de Paris (IAP), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), and Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Nuclear reaction, Thermonuclear fusion, 010504 meteorology & atmospheric sciences, Metallicity, chemistry.chemical_element, Astrophysics, 01 natural sciences, Stellar nucleosynthesis, Nucleosynthesis, cosmology: theory, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Helium, nuclear reactions, 0105 earth and related environmental sciences, Physics, abundances, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], nucleosynthesis, Astronomy and Astrophysics, Pop III stars, [PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Stars, chemistry, 13. Climate action, Space and Planetary Science, Carbon
Abstract

The effect of variations of the fundamental constants on the thermonuclear rate of the triple alpha reaction, 4He(αα,γ)12C, that bridges the gap between 4He and 12C is investigated. We follow the evolution of 15 and 60 M⊙ zero metallicity star models, up to the end of core helium burning. They are assumed to be representative of the first, Population III stars undergoing a very peculiar evolution due to the absence of initial CNO elements (zero metallicity). The calculated oxygen and carbon abundances resulting from helium burning can then be used to constrain the variations of the fundamental constants.

Published
2017

135. A compilation of charged-particle induced thermonuclear reaction rates

Author

Angulo, C., Arnould, M., Rayet, M., Descouvemont, P., Baye, D., Leclercq-Willain, C., Coc, A., Barhoumi, S., Aguer, P., Rolfs, C., Kunz, R., Hammer, J.W., Mayer, A., Paradellis, T., Kossionides, S., Chronidou, C., Spyrou, K., Degl'Innocenti, S., Fiorentini, G., Ricci, B., Zavatarelli, S., Providencia, C., Wolters, H., Soares, J., Grama, C., Rahighi, J., Shotter, A., and Lamehi Rachti, M.

Published
1999
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138. A microscopic approach to reactions of astrophysical interest

Author

Descouvemont, P., Baye, D., Araki, H., editor, Ehlers, J., editor, Hepp, K., editor, Kippenhahn, R., editor, Weidenmüller, H. A., editor, Wess, J., editor, Zittartz, J., editor, Beiglböck, W., editor, Hillebrandt, Wolfgang, editor, Kuhfuß, Rudolf, editor, Müller, Ewald, editor, and Truran, James W., editor

Published
1987
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148. Indirect study of12C(α,γ)16O reaction

Author

Hammache, F, primary, Oulebsir, N, additional, Roussel, P, additional, Pellegriti, M G, additional, Audouin, L, additional, Beaumel, D, additional, Bouda, A, additional, Descouvemont, P, additional, Fortier, S, additional, Gaudefroy, L, additional, Kiener, J, additional, Lefebvre-Schuhl, A, additional, and Tatischeff, V, additional

Published
2016
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