Physics
Scientific paper
Jul 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994metic..29q.474h&link_type=abstract
Meteoritics (ISSN 0026-1114), vol. 29, no. 4, p. 474
Physics
Chondrites, Cosmology, Surface Reactions, Capture Effect, Gamma Ray Spectrometers, Neutrons, Spallation
Scientific paper
Cosmogenic products by simple low-energy reactions like (n,gamma), (n,rho), (n,alpha), and (n,2n) are treated modifying those of spallation. In general, production, rho, of a spallation product can be expressed statistically by rho = fx k1' x (delta (A)')-k2', where f and delta(A)' are originated from target product relations, and k1' and k2' are shielding indexes. For low-energy products important regions are less than 30 MeV, and very low productions are observed in higher regions. In small objects and on the surface of meteoroids, low-energy fluxes are not in equilibria with those greater than 50 MeV, and deficiencies in these products are observed. Eberhardt et al. pointed out that He-3/Ne-21, or 3/21, and Ne-22/Ne-21, 22/21, in chondrites can be related linearly (Bern line). These and 3/22 have been used as shielding indexes. Even if 3/21 were equal, however, 22/21 at the center of smaller bodies are always slightly lower than those at the surface of larger objects, significantly deviating from the Bern line. Relations between 3/21 and 22/21 can be normalized to those at center, which is uniquely defined and reproducible. Neon-21 is produced partly by Mg-24(n,alpha) in addition to spallations. The latter, (22/21) spall., can be estimated statistically applying similar values of 'f' and delta-A' for (21)Nesp and (22)Nesp respectively. Along with shielding, the spallation term may decrease slowly, 0.7-0.6, but the (n,alpha) increases rapidly. This is the reason why 22/21 decreases by shielding. The relative deficiency of low-energy fluxes at the surface causes 22/21 to increase similarly. If shielding was extremely lower and the (n,alpha) contribution became negligible, 22/21 would reach asymptotically the maximum, and the depth dependency of 22/21 would disappear.
No associations
LandOfFree
Low-energy cosmogenic products in chondrites does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Low-energy cosmogenic products in chondrites, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Low-energy cosmogenic products in chondrites will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-822123