Pre-formation Probability of 5 He Cluster in Pre-equilibrium Mechanism

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In n + 10 B reactions, 5 He cluster emission has been discussed with the updated level scheme and the new optical model parameters. In this paper the reaction channels related to 5 He emission are listed in detail. By using the new reaction model for light nuclei, the double-differential cross sections of total outgoing neutrons for n + 10 B reactions at En = 14.2 MeV have been calculated, and the results agree fairly well with the measurements. Particularly, in the energy-angular spectra the contribution from the 5 He-emission to the total outgoing neutron double-differential cross sections has also been analyzed, and the partial energy-angular spectra of 60 • at En = 14.2 MeV have been given. The calculated results indicate that once the 5 He emission is taken into account, the fitting with the double-differential measurements of total outgoing neutrons at the low energy region could be improved. Therefore, to consider the 5 He emission properly in the reaction processes of light nuclei is necessary.

Section: Introductionmentioning

confidence: 99%

⁵ He Emission in Neutron-Induced ¹⁰ B Reactions

Wang

Duan

Yan

et al. 2006

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Double-Differential Cross Section of ⁵ He Emission

Yan

Duan

Zhang

et al. 2005

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The probability of 5He particle emission has been affirmed theoretically [J.S. Zhang, Science in China G47 (2004) 137]. In order to describe the 5He emission, the theoretical formula of the double-differential cross section of emitted 5He is to be established. Based on the pick-up mechanism, used for calculating the formula of d, t, 3He, α emissions, the theoretical formula of double-differential cross section of 5He is obtained, which is expressed in the form of Legendre coefficients. In the case of low incident energies, the configuration [J.S. Zhang, Science in China G47 (2004) 137; J.S. Zhang, Commun. Theor. Phys. (Beijing, China) 39 (2003) 83] is the dominant part in the reaction processes. The calculated result indicates that the forward peaked angular distribution of the composite particle emission is weaker than that of the emitted single nucleon due to pick-up nucleon from the Fermi sea. As an example, the reactions of n+14N have been calculated, and the Legendre coefficients of d, t, 3He, α, 5He emissions are obtained respectively. The results show that the forward tendency is decided by the average momentum per nucleon in the emitted composite particles. The larger the average momentum is, the stronger the forward tendency is.

Exciton-Dependent Pre-formation Probability of Composite Particles

Zhang¹,

Wang²,

Duan³

2007

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In Iwamoto–Harada model the whole phase space is full of fermions. When the momentum distributions of the exciton states are taken into account, the pre-formation probability of light composite particles could be improved, and the exciton state-dependent pre-formation probability has been proposed. The calculated results indicate that the consideration of the momentum distribution enhances the pre-formation probability of [1,m] configuration, and suppresses that of [l>1,m] configurations seriously.