High-precision mass measurements and production of neutron-deficient isotopes using heavy-ion beams at IGISOL

Abstract

An upgraded ion-guide system for the production of neutron-deficient isotopes with heavy-ion beams has been commissioned at the IGISOL facility with an 36 Ar beam on a nat Ni target. It was used together with the JYFLTRAP double Penning trap to measure the masses of 82 Zr, 84 Nb, 86 Mo, 88 Tc, and 89 Ru ground states and the isomeric state 88 Tc m. Of these, 89 Ru and 88 Tc m were measured for the first time. The precision of measurements of 82 Zr, 84 Nb, and 88 Tc was significantly improved. The literature value for 86 Mo was verified. The measured states in 88 Tc were compared to shell-model calculations and additional constraints on the spins and level scheme were obtained. The masses of 82 Mo and 86 Ru have been predicted using the measured masses of their mirror partners and theoretical mirror displacement energies, resulting in more tightly bound nuclei with smaller atomic mass uncertainties than reported in the literature.

Recent experiments at the JYFLTRAP Penning trap

“…Heavier neutron-deficient nuclei close to the N = Z line have been recently studied using an upgraded version of the heavy-ion ion-guide, HIGISOL [58], at IGISOL. The first online experiment with the upgraded system employed 222-MeV 36 Ar 8+ ions impinging into a nat Ni target [59]. High-precision mass measurements were performed with JYFLTRAP for 82 Zr, 84 Nb, 86 Mo, 88 Tc, 88 Tc m and 89 Ru [59,60].…”

“…The first online experiment with the upgraded system employed 222-MeV 36 Ar 8+ ions impinging into a nat Ni target [59]. High-precision mass measurements were performed with JYFLTRAP for 82 Zr, 84 Nb, 86 Mo, 88 Tc, 88 Tc m and 89 Ru [59,60]. Two of the masses, 88 Tc m and 89 Ru, were measured for the first time and the precisions of 82 Zr, 84 Nb and 88 Tc were improved significantly.…”

“…With the PI-ICR technique, the mass of the isomer could be determined for the first time. The isomer was measured against the ground state using the PI-ICR technique, yielding an excitation energy of E x = 70.4(31)keV [59]. The mass of the dominantly produced ground state was measured using the TOF-ICR technique, which together with the excitation energy yielded also a mass value for the isomer.…”

“…Shell-model calculations were also performed for comparison but those were highly sensitive to the used model space and interaction model (for details, see Ref. [59]).…”

“…In addition to the six atomic masses that were directly measured, the masses of 82 Mo and 86 Ru (T z = −1) were determined using theoretical mirror displacement energies (MDEs) and the directly measured masses of their respective mirror partners 82 Zr and 86 Mo (T z = +1) [59]. The resulting mass-excess values predict more tightly bound nuclei than literature [40], by more than 500 keV, and reduce the uncertainties of the predicted masses.…”