Electric monopole (E0) transitions studies in medium mass 50 ≤ A ≤ 72 nuclei

Abstract

The study of electric monopole transitions between two excited 0 plus states is important because the monopole strength carries vital information about the nuclear structure due to its direct link with the mean-square charge radius hr2i and quadrupole deformation parameter 2. Therefore, the measurement of internal conversion electrons ICE or internal pair formation IPF is crucial for E0 transition studies. Transitions between 0 plus states do not bear a change in angular momentum. Hence, single-photon emission is forbidden, but 0+ states can decay via conversion electrons or pair formation and two-photon emission which is mostly negligible. To implement E0 studies at iThemba Laboratory for Accelerator Based Sciences iThemba LABS, an electron spectrometer that uses a solenoidal magnetic field acting as a lens and a Si Li detector has been refurbished and characterized using calibration sources of ICE. Figures of merit have been extracted and compared with simulations. The spectrometer coupled with an array of LaBr3 Ce detectors and Low Energy Photon Spectrometers LEPS was successfully implemented for in-beam experiments.