Mass measurements of neutron-rich indium isotopes for r -process studies

Abstract

A new series of neutron-rich indium mass measurements are reported from the TITAN multiplereflection time-of-flight mass spectrometer (MR-TOF-MS). These mass measurements cover 125−134 In (N = 76 − 85) and include ground states as well as isomeric states. The masses of nuclei in this region are known to be of great importance for accurately modeling r-process nucleosynthesis, and the significance of the reported neutron-rich indium masses is discussed in this context. Results are compared with earlier experimental data where available as well as theoretical mass models. The measurements reported here include the first mass measurements of 133,134 In, as well as the first direct mass measurement of 132 In. The masses of 125−131 In ground states and several isomers were previously measured to higher precision by Penning trap mass spectrometry, which also resolved some low-lying isomers that could not be resolved in this work. The earlier Penning trap measurements serve as excellent cross-checks for the MR-TOF-MS measurements, and in some cases the MR-TOF-MS measurements improve the literature uncertainties of higher-lying isomer masses and excitation energies. A new isomeric state for 128 In, recently reported for the first time by the JYFLTRAP group, is also confirmed by the TITAN MR-TOF-MS, with a measured excitation energy of 1813(17) keV.

Sensitivity of Neutron-Rich Nuclear Isomer Behavior to Uncertainties in Direct Transitions

“…Version available at http://www.nndc.bnl.gov/ensarchivals/ accessed on 17 September 2020) [6]. Measurements of isomers and their properties continue to be a point of experimental interest for a variety of reasons, including not only as astrophysical model inputs, but also for applications in industry, medicine, and tests of fundamental nuclear physics [7][8][9][10][11][12][13][14][15][16][17]. For a recent review, see [18].…”

Mass measurements of $^{60-63}$Ga reduce x-ray burst model uncertainties and extend the evaluated $T=1$ isobaric multiplet mass equation

“…Detailed review of the available data sources showed that neither of the two reaction studies [106,107] which observed the higher-lying candidate level could assign it an unambiguous spin-parity or provide conclusive arguments for its identification as the IAS. The lower-lying candidate level was first observed in 58 Ni( 16 O, 14 C) 60 Zn reactions [108] and suggested as the IAS, based on the agreement of the observed excitation energy with a CDE prediction for E x ( 60 Zn i ). The same level was later observed as a cascade of βdelayed gamma rays in βγ-spectroscopy studies by Mazzocchi et.al [69] and Orrigo et al [70], which both identified it as the T = 1 IAS.…”

“…Providing mass separation powers of several 100 000 and background suppression factors as high as 10 4 [54], massselective retrapping allows one to leverage the characteristics of the isotope-separation on-line (ISOL) method, namely high rare isotope production yields at the expense of heavy isobaric contamination. After the first utilization in [56], the technique has been successfully used in several other on-line measurements at TITAN [57,58].…”

“…Such a sudden change in the staggering pattern could indicate isospin impurities [32] or a misidentified IAS. Currently, the experimental precision of this triplet is limited by the 50 keV uncertainty of the 58 Zn mass deduced from the measured Q-value of 58 Ni(π + , π − ) 58 Zn [115]. To exclude a possible anomaly, a direct mass measurement of 58 Zn with < 10 keV accuracy is desirable.…”

Decision Theory for the Mass Measurements at the Facility for Rare Isotope Beams

“…While this work was being completed, the 133 In mass was measured [33]. The next most informative measurement depends on the most likely r-process scenario, though clearly the (Z = 50,N = 82) region of the periodic table is a source of many informative mass measurements.…”