¹Takaharu Saito,¹Hiroshi Hidaka,²Shigekazu Yoneda
The Astrophysical Journal 955, 85 Open Access Link to Article [DOI 10.3847/1538-4357/acf37b]
¹Department of Earth and Planetary Sciences, Nagoya University, Nagoya 464-8601, Japan; ²Department of Science and Engineering, National Museum of Nature and Science, Tsukuba 305-0005, Japan

The isotopic compositions of Sm and Gd in eight eucrites—five from a desert, Dar al Gani (DaG) 380, DaG 391, DaG 411, DaG 443, and DaG 480, and three from nondesert areas, Juvinas, Millibillillie, and Stannern—were determined to understand the cosmic-ray exposure (CRE) history for each meteorite from the isotopic shifts of 149Sm–150Sm and 157Gd–158Gd caused by the neutron capture reactions induced by cosmic-ray irradiation. Seven of the eight samples, excepting DaG 443, show readily detectable isotopic shifts of Sm and Gd corresponding to neutron fluences in the range of (0.28–2.38) × 1015 neutrons cm−2. The degrees of Sm isotopic shifts for six of these seven eucrites can be consistently explained by the CRE age histogram of eucrites obtained in previous studies. Exceptionally, DaG 480 shows larger isotopic shifts of Sm than those expected from the CRE age histogram, suggesting a multiple-irradiation history, including irradiation on the parent body. However, there is no clear difference in the CRE conditions between DaG 480 and other eucrites from the parameter εSm/εGd to identify the difference in the thermalization degree of neutrons in association with the CRE conditions.

¹Kurt Marti,²Mario Fischer-Gödde,³Carina Proksche
The Astrophysical Journal 956, 7 Open Access Link to Article [DOI 10.3847/1538-4357/acee81]
¹Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093-0314, USA
²Universität zu Köln, Institut für Geologie und Mineralogie, Zülpicher Str. 49b, D-50674 Köln, Germany; mfisch48@uni-koeln.de
³Geo Zentrum Nordbayern, Friedrich-Alexander-Universität Erlangen-Nürnberg, Schlossgarten 5, D-91054 Erlangen, Germany

Anomalies in isotopic abundances of Mo and Ru in solar system matter were found to document variable contributions of the nucleosynthetic s-process component. We report isotopic relations of ⁹²Mo versus ¹⁰⁰Ru in meteorites from chondritic parent bodies, iron meteorites, and achondrites that reveal deviations from expected s-process abundance variations. We show that two p-process isotopes ⁹²Mo and ⁹⁴Mo require the presence of distinct p-process components in meteoritic materials. The nucleosynthetic origin of abundant magic (N = 50) p-process nuclides, covering the mass range of Zr, Mo, and Ru, has long been an enigma, but contributions by several recognized pathways, including alpha and νp-antineutrino reactions on protons, may account for the observed relatively large solar system abundances. Specific core-collapse supernovae explosive regions may carry proton-rich matter. Since Mo and Ru isotopic records in solar system matter reveal the presence of more than one nucleosynthetic p-process component, these records are expected to be helpful in documenting different explosive synthesis pathways and the implied galactic evolution of p-nuclides.

^1,4Oshtrakh, Michael I.,^1,2Maksimova, Alevtina A.,¹Petrova, Evgeniya V.,¹Chukin, Andrey V.,³Felner, Israel
Hyperfine Interactions 244, 22 Link to Article [DOI 10.1007/s10751-023-01830-9]
¹Institute of Physics and Technology, Ural Federal University, Ekaterinburg, 620002, Russian Federation
²Department of Chemistry and Biochemistry, University of South Carolina, Columbia, 29208, SC, United States
³Racah Institute of Physics, The Hebrew University, Jerusalem, 91904, Israel
⁴Department of Experimental Physics, Institute of Physics and Technology, Ural Federal University, Ekaterinburg, 620002, Russian Federation

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