Measuring the Thomas-Ehrman shifts in ¹⁶Ne by Aligning Reference States with no s-wave Character

Light mirror nuclei with states above particle-decay thresholds are powerful tools for measuring continuum effects that break isospin symmetry. One such effect, the Thomas-Ehrman shift, is expected to measurably reduce the energy of the ground and first 2⁺ excited states of ¹⁶Ne relative to its mirror nucleus, ¹⁶C, as these are expected to have s-wave content. Measuring the magnitude of this shift requires a pair of reference states in the mirror pair that have minimal s-wave content. The chosen reference state was the first 4⁺ level, which is known in ¹⁶C but has not been measured in ¹⁶Ne. An experiment was conducted at the Texas A&M Cyclotron Institute to populate the 4⁺ state of ¹⁶Ne by the 2-proton pickup by ¹⁴O on ⁹Be then measuring the subsequent two-proton decay via the invariant-mass method.