J. Hakala

Q values of the 76Ge and 100Mo double-beta decays

Penning trap measurements using mixed beams of 100 Mo - 100 Ru and 76 Ge - 76 Se have been utilized to determine the double-beta decay Q-values of 100 Mo and 76 Ge with uncertainties less than 200 eV. The value for 76 Ge, 2039.04(16) keV is in agreement with the published SMILETRAP value. The new value for 100 Mo, 3034.40(17) keV is 30 times more precise than the previous literature value, suffcient for the ongoing neutrinoless double-beta decay searches in 100 Mo. Moreover, the precise Q-value is used to calculate the phase-space integrals and the experimental nuclear matrix element of double-beta decay.

Evolution of the N=50 shell gap energy towards 78Ni.

Atomic masses of the neutron-rich isotopes (76-80)Zn, (78-83)Ga, (80-85)Ge, (81-87)As, and (84-89)Se have been measured with high precision using the Penning trap mass spectrometer JYFLTRAP at the IGISOL facility. The masses of (82,83)Ga, (83-85)Ge, (84-87)As, and 89Se were measured for the first time. These new data represent a major improvement in the knowledge of the masses in this neutron-rich region. Two-neutron separation energies provide evidence for the reduction of the N=50 shell gap energy towards germanium (Z=32) and a subsequent increase at gallium (Z=31). The data are compared with a number of theoretical models. An indication of the persistent rigidity of the shell gap towards nickel (Z=28) is obtained.

Precision mass measurements beyond ^{132}Sn: Anomalous behaviour of odd-even staggering of binding energies

Atomic masses of the neutron-rich isotopes (121-128)Cd, (129,131)In, (130-135)Sn, (131-136)Sb, and (132-140)Te have been measured with high precision (10 ppb) using the Penning-trap mass spectrometer JYFLTRAP. Among these, the masses of four r-process nuclei (135)Sn, (136)Sb, and (139,140)Te were measured for the first time. An empirical neutron pairing gap expressed as the odd-even staggering of isotopic masses shows a strong quenching across N = 82 for Sn, with a Z dependence that is unexplainable by the current theoretical models.

Precise atomic masses of neutron-rich Br and Rb nuclei close to the r-process path

Abstract.The Penning trap mass spectrometer JYFLTRAP, coupled to the Ion-Guide Isotope Separator On-Line (IGISOL) facility at Jyväskylä, was employed to measure the atomic masses of neutron-rich 85-92Br and 94-97Rb isotopes with a typical accuracy less than 10keV. Discrepancies with the older data are discussed. Comparison to different mass models is presented. Details of nuclear structure, shell and subshell closures are investigated by studying the two-neutron separation energy and the shell gap energy.

Total Absorption Spectroscopy Study of (92)Rb Decay: A Major Contributor to Reactor Antineutrino Spectrum Shape.

The antineutrino spectra measured in recent experiments at reactors are inconsistent with calculations based on the conversion of integral beta spectra recorded at the ILL reactor. (92)Rb makes the dominant contribution to the reactor antineutrino spectrum in the 5-8 MeV range but its decay properties are in question. We have studied (92)Rb decay with total absorption spectroscopy. Previously unobserved beta feeding was seen in the 4.5-5.5 region and the GS to GS feeding was found to be 87.5(25)%. The impact on the reactor antineutrino spectra calculated with the summation method is shown and discussed.

Q-value of the superallowed β decay of 62Ga

Abstract Masses of the radioactive isotopes 62Ga, 62Zn and 62Cu have been measured at the JYFLTRAP facility with a relative precision of better than 1.8 × 10 −8 . A Q EC value of ( 9181.07 ± 0.54 ) keV for the superallowed decay of 62Ga is obtained from the measured cyclotron frequency ratios of 62Ga 62Zn, 62Ga 62Ni and 62Zn 62Ni ions. The resulting F t -value supports the validity of the conserved vector current hypothesis (CVC). The mass excess values measured were ( − 51986.5 ± 1.0 ) keV for 62Ga, ( − 61167.9 ± 0.9 ) keV for 62Zn and ( − 62787.2 ± 0.9 ) keV for 62Cu.

Q values of the superallowed beta emitters 26Alm, 42Sc, and 46V and their impact on Vud and the unitarity of the Cabibbo-Kobayashi-Maskawa matrix.

The beta-decay Q(EC) values of the superallowed beta emitters 26Alm, 42Sc, and 46V have been measured with a Penning trap to a relative precision of better than 8 x 10(-9). Our result for 46V, 7052.72(31) keV, confirms a recent measurement that differed from the previously accepted reaction-based Q(EC) value. However, our results for 26Alm and 42Sc, 4232.83(13) keV and 6426.13(21) keV, are consistent with previous reaction-based values. By eliminating the possibility of a systematic difference between the two techniques, this result demonstrates that no significant shift in the deduced value of Vud should be anticipated.

Penning trap for isobaric mass separation at IGISOL

Abstract A cylindrical Penning trap has been built at the ion guide isotope separator facility IGISOL of the University of Jyvaskyla. The main goal of the Penning trap application is to purify low-energy radioactive ion beams. The aim is to make isobarically pure beams. The technical description is presented.

Isomeric states close to doubly magic 132Sn studied with JYFLTRAP

The double Penning trap mass spectrometer JYFLTRAP has been employed to measure masses and excitation energies for

Enhanced γ-Ray Emission from Neutron Unbound States Populated in β Decay.

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