Mass measurement of neutron-rich isotopes from51Ca to72Ni

Abstract

Abstract.The ground state masses of thirty-nine neutronrich nuclei from 51Ca to 72Ni have been measured using the Time-of-Flight Isochronous (TOFI) spectrometer. Eight of these masses have been measured for the first time and thirty-one are remeasurements of neutron-rich nuclei previously reported. Good agreement between these results and a previous TOFI experiment was observed except for the most neutron-rich isotopes of vanadium through iron with the present results being more bound and in better agreement with theory. The low binding energy of 68Ni, as indicated by an unreasonably low two-neutron separation energy, suggests the presence of a high-lying, long-lived isomeric state in this nucleus.

Surveying theN=40island of inversion with new manganese masses

“…The previous 62 Mn mass excess (in AME2003) of −48040(220) keV was the average value from three experiments by the TOFI group [44][45][46]. Our mass excess value is −48180.8(2.6) keV and agrees with the average of the previous measurements but with two orders of magnitude reduced uncertainty.…”

“…Due to its small uncertainty, the ISOLTRAP value is taken as the new tabulated mass. 61 Mn Previously, the mass of 61 Mn was measured in three experiments by the TOFI group at Los Alamos [44][45][46], with the average giving the mass excess value of −51560(230) keV. The ISOLTRAP measurement yields a value of −51741.9(2.3) keV, in agreement with the previous value but two orders of magnitude more precise.…”

“…Due to its high precision, ISOLTRAP carries 100% significance in the determination of the 62 Fe mass in the new AME. 63 Mn The mass of 63 Mn was previously measured in three different experiments with TOFI [44][45][46], giving an average mass excess value of −46350(260) keV. This value is 2σ away from our measured mass excess of −46886.9(3.7) keV.…”

“…The 60 Mn mass was also measured by the TOFI instrument at Los Alamos [44][45][46], yielding mass excesses of −52540(230), −52780(260), and −52520(250) keV, respectively. Our mass excess value does not agree with these measurements except for the second measurement.…”

“…Almost all ISOLTRAP masses are more bound than the previously measured masses. 61−65 Mn were determined by the Time-of-Flight Isochronous (TOFI) Spectrometer [44][45][46], using fragmented beams at high energies. This in-flight technique could easily have produced excited isomeric states that would not have been resolved by the spectrometer, which would result in less-bound masses.…”