Special Heavy Ion Discussion Group, Tuesday, 23 May 2023 at 3:30 pm

Jason Surbank, Michigan State University

Precision measurements of rare isotopes at the National Superconducting Cyclotron Laboratory

Abstract:

Precision measurements of rare isotopes yield interesting structural and decay properties of atomic nuclides. I will first discuss measurements of ground-state nuclear masses and their role in testing against anomalous terms in the Isobaric Mass Multiplet Equation (IMME), which is one prediction from the approximate isospin symmetry in nuclei. Penning Trap mass spectrometry techniques, such as those employed by the Low Energy Beam and Ion Trap (LEBIT) facility, most precisely measure the masses of exotic nuclei that must be produced at rare isotope facilities like the former National Superconducting Cyclotron Laboratory (NSCL). I will highlight two recent LEBIT measurements and their application to the IMME. I will then pivot to the curious case of the novel β-delayed proton (β^–p) decay. There is some conflict in the inferred β^–p decay probability of ¹¹Be, which is one of few nuclides capable of such a decay. The singular direct measurement of the ¹¹Be(β^–p) decay probability (b_p = 13(3)x10^–6) is in conflict with the most recent indirect measurement of the ¹¹Be→¹⁰Be total decay probability (b_total < 2x10^–6), with no obvious reconciliation. An independent, direct measurement of the ¹¹Be(β^–p) decay was performed at NSCL. A Bayesian analysis code was developed to model the relevant ¹¹Be charged-particle spectra, including detector effects and portions of the large, ~3% β^–α background. We infer the novel decay probability with a precision of 4x10^–6. I will conclude with details of a new experimental collaboration that intends to perform an independent measurement of the indirect ¹¹Be→¹⁰Be total decay probability and the first measurement of the ¹⁵C→¹⁴C decay probability to <1x10^–7.

This work has been supported by the U. S. Department of Energy under Award No.: DE-SC0016052 and the U. S. National Science Foundation under Award No.: 1565546 and 1913554.