Fission resonances observed in the $$^{237}$$Np(d,pf) reaction and the fission barrier topology of $$^{238}$$Np

• Published in: The European physical journal. A, Hadrons and nuclei Vol. 58; no. 2
• Main Authors: Csige, Lóránt, Csatlós, Margit, Faestermann, Thomas, Habs, Dieter, Hunyadi, Mátyás, Krasznahorkay, Attila J., Thirolf, Peter G., Tornyi, Tamás G., Wirth, Hans-F.
• Format: Journal Article
• Language: English
• Published: 01-02-2022
• ISSN: 1434-6001; 1434-601X
• DOI: 10.1140/epja/s10050-022-00668-z

The fission probability of
$$^{238}$$
238
Np was measured as a function of the excitation energy in the energy range of E
$$^* = 5.4 - 6.2$$
∗
=
5.4
-
6.2
MeV in order to search for transmission fission resonances. A radioactive
$$^{237}$$
237
Np target was bombarded with deuterons of E
$$_d$$
d
= 12 MeV, whereas the energy of the protons was analyzed with a superior resolution of
$$\varDelta $$
Δ
E = 8 keV. The experiment was performed at the Tandem accelerator of the Maier-Leibnitz Laboratory in Garching employing the
$$^{237}$$
237
Np(d,pf) reaction. A group of fission resonances has been observed at excitation energies between E
$$^* = 5.5 - 5.8$$
∗
=
5.5
-
5.8
MeV, which could be ordered into three (superdeformed) rotational bands with a rotational parameter of
$$\hbar ^2/2\varTheta = 3.507$$
ħ
2
/
2
Θ
=
3.507
keV, and identified as the first direct observation of transition states composing rotational bands in an odd-odd nucleus as they appear above the top of the outer fission barrier. Nuclear reaction code (
talys1.95
) calculations were also performed to extract the multi-humped fission barrier parameters of
$$^{238}$$
238
Np by fitting them to the experimental data of the present (d,pf) and previous (n,f) experiments. The extracted barrier parameters also support the above interpretation of the observed resonances.