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Résumé |
Recent developments in nuclear structure approaches offer a great
mean to improve various aspects of nuclear reaction modeling and to
further understand reaction mechanisms from a microscopic point of
view. Recently, direct and pre-compound nucleon emission, for nucleon
induced reaction on spherical and axially deformed nuclei, have been
successfully modeled [1] using a description of target states provided
by fully consistent axially-symmetric deformed quasi-particle
random-phase approximation (QRPA) calculations [2]. Direct inelastic
scattering to target excitations built from one-phonon QRPA states
accounted simultaneously for direct inelastic scattering to discrete
states, and pre-equilibrium emission as far as second order processes,
that involve more complex excitations such as two-phonon states, and
multiple emission remain negligible. The QRPA nuclear structure
approach has also been applied recently to determine, for a large pannel of even-even nuclei,
E1 and M1 photon strength functions [3],
that play a key-role in the modeling of statistical reactions.\\
We will review the status on the ongoing work on
direct/pre-compound neutron emission for neutron induced reaction
below 20~MeV for even-even actinides.
Target states are described as rotational bands built from each state in the
target intrinsic frame, described as QRPA one-phonon excitation of the
intrinsic correlated ground state. QRPA excitations which display a
collective character can thus be viewed as vibrational band heads.
Couplings between states of the GS band and states belonging to an
excited band are accounted for within a coupled channel framework.
Our approach in then applied to the modeling of (n,n'$\gamma$)
reactions and for both intra- and
inter-band gamma transitions [4]. For these reactions, the role played by the present
microscopic approach for direct/pre-equilibrium emission is discussed.
We finally focus on the impact on the determination of (n,n'$\gamma$) cross
sections of newly calculated QRPA E1- and M1-photon strength
functions, that enter the description of statistical decay from compound nucleus states
in the continuum.\\
[1] M. Dupuis, E. Bauge, S. Hilaire, F. Lechaftois, S. P\'eru, N. Pillet and C. Robin, Eur. Phys. J. A, 51 12 (2015) 168.\\[.1cm]
[2] S. P\'eru,G. Gosselin, M. Martini, M. Dupuis, S. Hilaire, and J.-C. Devaux, Phys. Rev. C 014314 (2011).\\[.1cm]
[3] S. Goriely, S. Hilaire, S. P\'eru, M. Martini, I. Deloncle, and F. Lechaftois
Phys. Rev. C 94, 044306 (2016); M. Martini, S. P\'eru, S. Hilaire, S. Goriely, and F. Lechaftois, Phys. Rev. C 94, 014304 (2016).\\[.1cm]
[4] M. Dupuis, S. Hilaire, S. P\'eru, E. Bauge, M. Kerveno, P. Dessagne and G. Henning EPJ Web Conf., 146 (2017) 12002. |
