Precision mass measurements of magnesium isotopes and implications for the validity of the isobaric mass multiplet equation

Abstract

If the mass excess of neutron-deficient nuclei and their neutron-rich mirror partners are both known, it can be shown that deviations of the Isobaric Mass Multiplet Equation (IMME) in the form of a cubic term can be probed. Such a cubic term was probed by using the atomic mass of neutron-rich magnesium isotopes measured using the TITAN Penning trap and the recently measured proton-separation energies of 29 Cl and 30 Ar. The atomic mass of 27 Mg was found to be within 1.6σ of the value stated in the Atomic Mass Evaluation. The atomic masses of 28,29 Mg were measured to be both within 1σ, while being 7 and 33 times more precise, respectively. Using the 29 Mg mass excess and previous measurements of 29 Cl we uncovered a cubic coefficient of d = 28 (7) keV, which is the largest known cubic coefficient of the IMME. This departure, however, could also be caused by experimental data with unknown systematic errors. Hence there is a need to confirm the mass excess of 28 S and the one-neutron separation energy of 29 Cl, which have both come from a single measurement. Finally, our results were compared to ab initio calculations from the valence-space in-medium similarity renormalization group, resulting in a good agreement.

Nonempirical Interactions for the Nuclear Shell Model: An Update

“…IMSRG and CCEI/SMCC emerged (139,140,142,143,179). The VS-IMSRG, in particular, has been widely used to compute ground and excited-state energies (129,142,143,(225)(226)(227)(228)(229)(230)(231)(232)(233)(234)(235)(236)(237)(238), although theoretical uncertainties stemming from the method still prove challenging (see Sec. 6).…”

First Penning trap mass measurement of $^{36}$Ca

“…A measurement of 28 S will finish the A = 28 quintet, giving IMME coefficients from A = 20 − 36 in regular steps of δA = 4. Additionally, paired with recent protonseparation energy measurements [33], a high-precision measurement of 28 S would update the mass of 29 Cl and may clarify the source of the large T = 5/2, A = 29 d coefficient (d = 28(7) keV), the largest measured cubic coefficient across all masses and isospin [34]. Meanwhile, further insight into the source of the positive experimental d coefficient in A = 32 may explain the apparent breakdown of the higher mass T = 2 GIMME predictions.…”

Isobaric multiplet mass equation within nuclear density functional theory

“…. For higher multiplets (T>1), there is an active ongoing debate if higher-order terms, proportional to T z 3 or T z 4 , are required, see [37,38] for brief recent reviews.…”

“…Of course, for triplets (T = 1), nuclear masses can always be trivially described by a parabolic dependence on T z , so then the information carried by the IMME coefficients is exactly the same as that contained in the displacement energies discussed above, with MDE = 2T a A,T,I = 2T 2 c. For higher multiplets (T > 1), there is an active ongoing debate if higher-order terms, proportional to T 3 z or T 4 z , are required, see Refs. [37,38] for brief recent reviews.…”