Postdoctoral position - Cross section measurements for the p-process nucleosynthesis

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Short description

The LIO Laboratory of Excellence (LabEx) proposes a 2-year post-doctoral position.

Starting date: between September the 1st, 2022 and November the 1st, 2022

The net salary (+social benefits) will depend on experience. A €3,000 annual package for travels and equipment will be allotted.

Research project

In the Universe chemical composition, several elements beyond iron are observed to have stable isotopes situated on the proton-rich side of the stability valley: these isotopes are called p-nuclei. Their specificity is that they cannot have been produced by neutron-capture processes, contrary to the majority of nuclei heavier than iron. The nucleosynthesis mechanism that leads to the formation of p-nuclei is called the p-process. According to the dominant astrophysical scenario, it takes place during core-collapse supernovae, and mainly involves the photodisintegration of a seed population of nuclei originating from the neutron rich side of the stability valley. First, several neutrons are expelled by (γ,n) reactions, but the final abundance of the different p-nuclei crucially depends on (γ,p) and (γ,α) reactions that occur in the end. They are an essential input for the nucleosynthesis calculations that aim to test different astrophysical models to reproduce the observed abundance of p-nuclei.

Globally, the p-process involves a network around 2000 nuclei and 20000 reactions, most of which cannot be measured experimentally. Nucleosynthesis calculations have to rely on theoretical calculations of cross sections based on the Hauser-Feshbach statistical model. The nuclear statistical parameters that allow to perform such calculations are the optical model potentials, the level density and the gamma strength, which are themselves described by different models. Experimental data are much needed to better constrain these models. Especially, it is repeatedly mentioned in the literature that the lack of experimental knowledge on the alpha-nucleus optical potential at energy of astrophysical interest (namely far below the Coulomb barrier) hinders the progress in the nucleosynthesis modeling. Our project is focused on the measurement of cross sections that are crucial to improve the knowledge of astrophysical reaction rates. 

We have selected several key reactions for this purpose. The main objective of our project is to perform alpha and proton capture experiments at the NFS-SPIRAL2 facility, whose high-intensity alpha and proton beams in the relevant energy range offers a unique opportunity to access the very low cross sections that are needed in the astrophysical context. These measurements will involve two types of techniques: if the lifetime of the reaction product allows, the well-known activation technique can be used ; else, in-beam techniques have to be employed to count the gamma rays produced instantaneously after the reaction. We plan to perform such experiments around 2023. Meanwhile, preparatory experiments should be performed at medium-scale facilities, to better control the classical experimental issues before facing the new challenges associated with very high intensity. Furthermore, the knowledge of alpha-nucleus optical potentials also need to be increased by complementary alpha-scattering measurements: the exploration of isotopic and deformation effects should be particularly enlightening, and several such measurements will take place in the next years, for instance at the Orsay Split-Pole facility.

Research field(s)

Experimental nuclear astrophysics / p-process nucleosynthesis

Supervisor and contact


Institut de Physique des 2 Infinis de Lyon

Campus LyonTech la Doua, bâtiment Dirac

4 rue Enrico Fermi, 69622 Villeurbanne


TEL: +33 (0)4 72 43 13 41



Institut de Physique des 2 Infinis de Lyon

Campus LyonTech la Doua, bâtiment Dirac

4 rue Enrico Fermi, 69622 Villeurbanne


TEL: +33 (0)4 72 43 13 46


Working environment

Job location and description

Most of the work is performed in the IP2I Laboratory and consists in conducting an experimental research program using international infrastructures

The recruited candidate will have the charge to develop our p-process program and thus she/he will have to manage the experiments already accepted and the ones to be proposed. It requires also to perform data analysis and simulations in close collaboration with a PhD student. As well,  the candidate will have the charge to strengthen our collaboration with the “Laboratoire de Géologie de Lyon – Terre, Planètes, Environnement” which is working also on the p-process though measurements of compositions of micrometeorites. 


The IP2I « Matière Nucléaire » (Nuclear Matter) group, composed of six permanent members and two students, is involved in experimental nuclear structure & nuclear astrophysics studies. C. Ducoin (enseignante-chercheuse, Université de Lyon) and O. Stézowski (chercheur, CNRS) are co directors of the thesis of Y. Demane (2020-2023) who is working on a subject directly linked with the postdoc program. N. Millard (enseignante-chercheuse, Université de Lyon, IP2I « Matière Nucléaire » group) is also strongly involved in the p-process program and will be then a close collaborator.

The recruited candidate will also interact with our local/national/international collaborators on the p-process project located mostly at GANIL, IJCLab and LGLTPE.   

Allocated resources (technical facilites, computing…)

Most of the experimental work is performed using international facilities such as ALTO at Orsay or NFS-SPIRAL2 at GANIL/Caen using existing (split-pole, gamma-ray) detectors. The computing resources are provided by IP2I, possibly, if mandatory, by CCIN2P3.   

Recent publications of the team

Gamma-ray intensities in multi-gated spectra - Camille Ducoin, Guillaume Maquart, Olivier Stézowski 

NIM A 931, 105-120 (2019)

DOI:   https://doi.org/10.1016/j.nima.2019.04.035


Backbending in the pear-shaped 22390Th nucleus: Evidence of a high-spin octupole to quadrupole shape transition in the actinides - G.Maquart et al.,

Phys.Rev. C 95, 034304 (2017)

DOI:     10.1103/PhysRevC.95.034304 

Description of LabEx LIO

In 2011, The Lyon Institute of Origins LabEx was selected following the first “Laboratory of Excellence” call for projects, part of the “Investissement d’Avenir” program for forward-looking research. It is one of 12 LabExes supported by the University of Lyon community of universities and establishments (COMUE). LIO brings together more than 200 elite researchers recruited throughout the word and forming 18 research teams from four laboratories in the Rhône-Alps region, all leaders in their fields, under the auspices of the University Claude Bernard Lyon 1 (UCBL), the Ecole Normale Supérieure de Lyon, and the CNRS. LIO’s goal is to explore questions about our origins, operating in a broad field of study that ranges from particle physics to geophysics, and includes cosmology, astrophysics, planetology and life.

Selection process

Qualifications / Skills / Education & Research requirements

The ideal candidate must hold a PhD in experimental nuclear physics/astrophysics, should have facilities in conducting an experimental program involving large collaborations and international facilities: it thus required to travel on a regular basis. Skills in running complex codes, nuclear reaction codes (Ex: TALYS) and simulation codes (Ex: GEANT4), and in programming (C++,python) are very welcome. Experience in experimental gamma-ray spectroscopy (with very high resolution Germanium detectors or gamma-ray calorimeters) is an advantage. 

Application deadline

April the 1st, 2022

Requested documents for application

Applicants must email a CV, a statement of interest, a letter of recommendation and contact details for 2-3 references at c.ducoin@ipnl.in2p3.fr and o.stezowski@ip2i.in2p3.fr before April the 1st, 2022. 

Candidates on the short list will be informed by the end of April. They will be interviewed in May. 

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Job details

Postdoctoral position - Cross section measurements for the p-process nucleosynthesis
4 Rue Enrico Fermi Villeurbanne, France
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In 2011, Lyon Institute of Origins (LIO) LabEx was selected following the first “Laboratory of Excellence” call for projects, part of the “Investis...

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