Speaker
Description
One of the fundamental properties of excited nuclear quantum states is their lifetime which is related to the level width. A precise measurement of this width for key-states of light isotopes is of fundamental importance. Level widths and decay strengths are not only important observables for classifying the structure of atomic nuclei, but they can also serve as a crucial test of the modeling of nuclear forces and of nuclear quantum transitions [1]. In particular, transition probabilities in light isotopes can help us understand the importance of 2- and 3-body interactions in the framework of chiral Effective Field Theory and of the role of 2-body currents (2BC) in decay transitions. However, for many isotopes the width of low-lying levels is not measured with a sufficient precision.
A well known technique to obtain lifetimes and level widths in a wide range of energies is the use of Nuclear Resonance Fluorescence (NRF) and Self-Absorption (SA) [2]. In recent years a new technique called Relative Self-Absorption (RSA) has been developed at TU Darmstadt [1, 2]. It has been demonstrated that this technique provides reduced systematic uncertainty for values of the level widths compared to traditional NRF and SA. However, the analysis of the data at this level of precision required already information on the details of the thermal motion of the nuclei of interest in the target, such as the Debye temperature of the material.
In this contribution an advanced RSA technique will be presented, the Temperature-dependent RSA (TRSA), which overcomes the limitations of the RSA related to the pre-existing knowledge of the thermal motion properties of the targets used in the measurement [3]. In TRSA, measurements in multiple target-temperatures, from a 70 K to 500 K, are performed. The Debye temperature of the target materials and the level width of the state of interest are measured simultaneously. The theoretical analysis, which will be presented, shows that this method reduces the systematic uncertainties of the measured transition matrix elements, down to the level of some parts in a thousand, by avoiding systematical uncertainties of theoretical treatments of thermal material properties.
The features of the temperature-control target system which is under developed in the Institute for Nuclear Physics of the Technische Universität Darmstadt will be presented.
This research is supported in part by the State of Hesse within the LOEWE research project “Nuclear Photonics” and the Deutsche Forschungsgemeinschaft – Project-ID 279384907 – SFB 1245.
[1] U. Friman-Gayer et al., Phys. Rev. Lett. 126, 102501 (2021).
[2] A. Zilges, D. Balabanski, J. Isaak, N. Pietralla, Prog. Part. Nucl. Phys. 122, 103903 (2022).
[3] R. Moreh et al. Phys. Rev. B 56, 187 (1997).
