Speaker
Description
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 first 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.
Relative strengths of these couplings, for various neutron
incident energies, transfer angular momenta, and intrinsic states
properties, are analyzed in order to define the relevent coupled channel
scheme that is needed in the determination of direct/pre-compound cross-sections.\
Our approach in then applied to the modeling of (n,n'$\gamma$)
reactions for various even-even actinides 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. Thus, 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.\[1cm]
{\footnotesize
\noindent
[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.}
