Investigation of the potential ultralow Q -value β -decay candidates Sr89 and Ba

Abstract

Background: Ultra-low Q-value β-decays are interesting processes to study with potential applications to nuclear β-decay theory and neutrino physics. While a number of potential ultra-low Q-value β-decay candidates exist, improved mass measurements are necessary to determine which of these are energetically allowed.Purpose: To perform precise atomic mass measurements of 89 Y and 139 La. Use these new measurements along with the precisely known atomic masses of 89 Sr and 139 Ba and nuclear energy level data for 89 Y and 139 La to determine if there could be an ultra-low Q-value decay branch in the β-decay of 89 Sr → 89 Y or 139 Ba → 139 La.Method: High-precision Penning trap mass spectrometry was used to determine the atomic mass of 89 Y and 139 La, from which β-decay Q-values for 89 Sr and 139 Ba were obtained.Results: The 89 Sr → 89 Y and 139 Ba → 139 La β-decay Q-values were measured to be QSr = 1502.20(0.35) keV and QBa = 2308.37(0.68) keV. These results were compared to energies of excited states in 89 Y at 1507.4(0.1) keV, and in 139 La at 2310(19) keV and 2313(1) keV to determine Q-values of -5.20(0.37) keV for the potential ultra-low β-decay branch of 89 Sr and -1.6(19.0) keV and -4.6(1.2) keV for those of 139 Ba. Conclusion:The potential ultra-low Q-value decay branch of 89 Sr to the 89 Y (3/2 − , 1507.4 keV) state is energetically forbidden and has been ruled out. The potential ultra-low Q-value decay branch of 139 Ba to the 2313 keV state in 139 La with unknown J π has also been ruled out at the 4σ level, while more precise energy level data is needed for the 139 La (1/2 + , 2310 keV) state to determine if an ultra-low Q-value β-decay branch to this state is energetically allowed. * sandler@nscl.msu.edu 1 The energy of the 115 Sn (3/2 + ) state was recently measured more precisely to be 497.342 (3) keV [7].

Direct measurement of the mass difference of As72−Ge72 rules out AsZhuang1, Eronen2, Roubin3 et al. 2021Phys. Rev. C180601View full textAdd to dashboardCite

“…Several potential ultra-low Q-value β -decay candidates have recently been studied via PTMS, for example 89 Sr, 131 Cs, 135 Cs and 139 Ba [28][29][30]. Among them, one promising candidate of the first-forbidden unique β − -decay transition, 135 Cs (7/2 + , ground state)→ 135 Ba (11/2 − , second excited state), was confirmed to be an ultra-low Q-value decay channel.…”

Precise Q value measurements of $^{112,113}$Ag and $^{115}$Cd with the Canadian Penning trap for evaluation of potential ultra-low Q value $β$-decays

“…where M p and M d are the mass of the parent and daughter atoms, respectively, and m e is the mass of the electron. The conversion factor from atomic mass units to keV, 1 u = 931 494.102 42 (28) keV/c 2 from Ref. [44] was used.…”

“…In collaboration with the LEBIT group at the National Superconducting Cyclotron Laboratory, we recently investigated and ruled out two candidates identified in Ref. [27]: 89 Sr and 139 Ba [28]. The JYFLTRAP group recently ruled out potential UL Q value decays in 72 As [29], and showed that 159 Dy does have an electron capture decay branch to an excited state in the daughter with a Q UL value of around 1 keV [30].…”

Status of CHIP-TRAP: The Central Michigan University High-Precision Penning Trap

“…Measurements at Penning trap facilities with ions from a LAS have spanned the nuclear chart from, for example, 6,7 Li [30] to 249 Cf [28]. Ions from a LAS serve as reference masses for on-line measurements with short-lived isotopes, calibrants for tuning a system and investigating systematics, and as the ions of interest for nuclear and neutrino physics studies, e.g., [31][32][33][34][35][36][37].…”