Speaker
Description
The outcome of any possible nucleosynthesis scenario is strongly affected by the photodisintegration of nuclei through (γ, N) and (γ, np) channels for Eγ > 10MeV to a few hundred MeV. Though there is a wide range of phenomenological models for the estimation of excitation functions in this energy region, the exact photodisintegration mechanism is not well understood. The shell-model based approaches have not been successful even for the light nuclei of astrophysical importance like 6Li [1]. By extending the Independent PAir Model [2] (IPAM), a SRC-based approach is employed to calculate the photo-disintegration of light nuclei in quasideuteron region. Combining the Gunn-Irving photo-disintegration for α-cluster [3], the proposed approach is used to calculate the total photo-disintegration cross-sections for Eγ between 10 to 140 MeV for many of the N=Z light nuclei from 4He to 40Ca. Contrary to general perception, the quasideuteron photo-disintegration contribution starts in the GDR region itself [4] and dominates at Eγ > 50 MeV. Along with many interesting new insights, the derivation of the Levinger [5] formula is obtained without any additional assumption. A significant fraction of the photo-disintegration cross-section in GDR region may be accounted by contribution of quasi-α degree of freedom which decreases for higher Eγ. The present work suggests an alternative and viable description of photodisintegration for N=Z nuclei in terms of np-SRCs/quasideuteron structures and their paired counterparts.
References
[1] S. Bacca, and S. Pastore, Electromagnetic reactions on light nuclei, J. Phys. G: Nuc. Part. Phys. 41, 123002 (2014).
[2] L. C. Gomes, J. D. Walecka, and V. F. Weisskopf, Properties of nuclear matter, Ann. Phys. 3, 241 (1958).
[3] J. C. Gunn, and J. Irving, The photo-electric disintegration of three- and four-particle nuclei, Phil. Mag. 42 1353 (1951).
[4] A.Veyssière, H. Beil, R. Bergère, P. Carlos, A. Leprêtre, A. De Miniac, A study of the photoneutron contribution to the giant dipole resonance of s-d shell nuclei, Nuc. Phys. A 227, 513 (1974).
[5] J. S. Levinger, The high energy nuclear photoeffect, Phys. Rev. 84, 43 (1951).
