Three beta-decaying states in 128In and 130In resolved for the first time using Penning-trap techniques

Isomeric states in 128In and 130In have been studied with the JYFLTRAP Penning trap at the IGISOL facility. By employing state-of-the-art ion manipulation techniques, three different beta-decaying states in 128In and 130In have been separated and their masses measured. JYFLTRAP was also used to select the ions of interest for identification at a post-trap decay spectroscopy station. A new beta-decaying high-spin isomer feeding the isomer in 128Sn has been discovered in 128In at 1797.6(20) keV. Shell-model calculations employing a CD-Bonn potential re-normalized with the perturbative G-matrix approach suggest this new isomer to be a 16⁺ spin-trap isomer. In 130In, the lowest-lying (10⁻) isom…

Direct determination of the atomic mass difference of the pairs As 76 − Se 76 and Tb 155 − Gd 155 rules out As 76 and Tb 155 as possible candidates for electron (anti)neutrino mass measurements

Direct measurement of the mass difference of $^{72}$As-$^{72}$Ge rules out $^{72}$As as a promising $\beta$-decay candidate to determine the neutrino mass

We report the first direct determination of the ground-state to ground-state electron-capture $Q$-value for the $^{72}$As to $^{72}$Ge decay by measuring their atomic mass difference utilizing the double Penning trap mass spectrometer, JYFLTRAP. The $Q$-value was measured to be 4343.596(75)~keV, which is more than a 50-fold improvement in precision compared to the value in the most recent Atomic Mass Evaluation 2020. Furthermore, the new $Q$-value was found to be 12.4(40)~keV (3.1 $\sigma$) lower. With the significant reduction of the uncertainty of the ground-state to ground-state $Q$-value value combined with the level scheme of $^{72}$Ge from $\gamma$-ray spectroscopy, we confirm that th…

Direct determination of the excitation energy of the quasistable isomer 180mTa

180mTa is a naturally abundant quasistable nuclide and the longest-lived nuclear isomer known to date. It is of interest, among others, for the search for dark matter, for the development of a γ laser, and for astrophysics. So far, its excitation energy has not been measured directly but has been based on an evaluation of available nuclear reaction data. We have determined the excitation energy of this isomer with high accuracy using the Penning-trap mass spectrometer JYFLTRAP. The determined mass difference between the ground and isomeric states of 180Ta yields an excitation energy of 76.79(55) keV for 180mTa. This is the first direct measurement of the excitation energy and provides a bet…

Observation of an ultralow- Q -value electron-capture channel decaying to As75 via a high-precision mass measurement

Observation of an ultralow-Q-value electron-capture channel decaying to 75As via a high-precision mass measurement

A precise determination of the atomic mass of 75As has been performed utilizing the double Penning trap mass spectrometer, JYFLTRAP. The mass excess is measured to be −73035.519(42)keV/c2, which is a factor of 21 more precise and 1.3(9)keV/c2 lower than the adopted value in the newest Atomic Mass Evaluation (AME2020). This value has been used to determine the ground-state–to–ground-state electron-capture decay Q value of 75Se and β− decay Q value of 75Ge, which are derived to be 866.041(81) keV and 1178.561(65) keV, respectively. Using the nuclear energy-level data of 860.00(40) keV, 865.40(50) keV (final states of electron capture), and 1172.00(60) keV (final state of β− decay) for the exc…

Radioactive ion beam manipulation at the IGISOL-4 facility

The IGISOL-4 facility in the JYFL Accelerator Laboratory of the University of Jyvaskyla (JYFL-ACCLAB) produces low-energy radioactive ion beams, primarily for nuclear spectroscopy, utilizing an ion guide-based, ISOL-type mass separator. Recently, new ion manipulation techniques have been introduced at the IGISOL-4 including the application of the PI-ICR (Phase-Imaging Ion Cyclotron Resonance) technique at the JYFLTRAP Penning trap, as well as commissioning of a Multi-Reflection Time-Of-Flight (MR-TOF) separator/spectrometer. The successful operation of the MR-TOF also required significant improvement of the Radio-Frequency Quadrupole (RFQ) cooler and buncher device beam pulse time structure…

Dy159 Electron-Capture: A New Candidate for Neutrino Mass Determination

International audience; The ground state to ground state electron-capture Q value of Dy159 (3/2-) has been measured directly using the double Penning trap mass spectrometer JYFLTRAP. A value of 364.73(19) keV was obtained from a measurement of the cyclotron frequency ratio of the decay parent Dy159 and the decay daughter Tb159 ions using the novel phase-imaging ion-cyclotron resonance technique. The Q values for allowed Gamow-Teller transition to 5/2- and the third-forbidden unique transition to 11/2+ state with excitation energies of 363.5449(14) keV and 362.050(40) keV in Tb159 were determined to be 1.18(19) keV and 2.68(19) keV, respectively. The high-precision Q value of transition 3/2-…

Direct measurement of the mass difference of 72As-72Ge rules out 72As as a promising β-decay candidate to determine the neutrino mass

Preprint of paper published on Physical Review C We report the first direct determination of the ground-state to ground-state electron-capture Q-value for the 72As to 72Ge decay by measuring their atomic mass difference utilizing the double Penning trap mass spectrometer, JYFLTRAP. The Q-value was measured to be 4343.596(75) keV, which is more than a 50-fold improvement in precision compared to the value in the most recent Atomic Mass Evaluation 2020. Furthermore, the new Qvalue was found to be 12.4(40) keV (3.1 σ) lower. With the significant reduction of the uncertainty of the ground-state to ground-state Q-value value combined with the level scheme of 72Ge from γ-ray spectro…

Coulomb excitation of Rn-222

The nature of quadrupole and octupole collectivity in 222Rn was investigated by determining the electric-quadrupole (E2) and octupole (E3) matrix elements using subbarrier, multistep Coulomb excitation. The radioactive 222Rn beam, accelerated to 4.23 MeV/u, was provided by the HIE-ISOLDE facility at CERN. Data were collected in the Miniball γ-ray spectrometer following the bombardment of two targets, 120Sn and 60Ni. Transition E2 matrix elements within the ground-state and octupole bands were measured up to 10ℏ and the results were consistent with a constant intrinsic electric-quadrupole moment, 518(11)efm2. The values of the intrinsic electric-octupole moment for the 0+→3− and 2+→5− transi…

Direct determination of the atomic mass difference of the pairs 76As−76Se and 155Tb−155Gd rules out 76As and 155 Tb as possible candidates for electron (anti)neutrino mass measurements

The first direct determination of the ground-state–to–ground-state Q values of the β− decay 76As→76Se and the electron-capture decay 155Tb→155Gd was performed utilizing the double Penning trap mass spectrometer JYFLTRAP. By measuring the atomic mass difference of the decay pairs via the phase-imaging ion-cyclotron-resonance technique, the Q values of 76As→76Se and 155Tb→155Gd were determined to be 2959.265(74) keV and 814.94(18) keV, respectively. The precision was increased relative to earlier measurements by factors of 12 and 57, respectively. The new Q values are 1.33 keV and 5 keV lower compared to the values adopted in the most recent Atomic Mass Evaluation 2020. With the newly determi…

Observation of an ultralow- Q -value electron-capture channel decaying to As 75 via a high-precision mass measurement

Direct determination of the excitation energy of the quasistable isomer Ta180m

International audience; Ta180m is a naturally abundant quasistable nuclide and the longest-lived nuclear isomer known to date. It is of interest, among others, for the search for dark matter, for the development of a γ laser, and for astrophysics. So far, its excitation energy has not been measured directly but has been based on an evaluation of available nuclear reaction data. We have determined the excitation energy of this isomer with high accuracy using the Penning-trap mass spectrometer JYFLTRAP. The determined mass difference between the ground and isomeric states of Ta180 yields an excitation energy of 76.79(55) keV for Ta180m. This is the first direct measurement of the excitation e…

Novel Penning-trap techniques reveal isomeric states in $^{128}$In and $^{130}$In for the first time

Isomeric states in $^{128}$In and $^{130}$In have been studied with the JYFLTRAP Penning trap at the IGISOL facility. By employing novel ion manipulation techniques, different states were separated and masses of six beta-decaying states were measured. JYFLTRAP was also used to select the ions of interest for identification at a post-trap decay spectroscopy station. A new beta-decaying high-spin isomer feeding the $15^-$ isomer in $^{128}$Sn has been discovered in $^{128}$In at $1797.6(20)$ keV. Shell-model calculations employing a CD-Bonn potential re-normalized with the perturbative G-matrix approach suggest this new isomer to be a $16^+$ spin-trap isomer. In $^{130}$In, the lowest-lying $…

Dy 159 Electron-Capture: A New Candidate for Neutrino Mass Determination

Three beta-decaying states in In and In resolved for the first time using Penning-trap techniques

Isomeric states in $^{128}$In and $^{130}$In have been studied with the JYFLTRAP Penning trap at the IGISOL facility. By employing state-of-the-art ion manipulation techniques, three different beta-decaying states in $^{128}$In and $^{130}$In have been separated and their masses measured. JYFLTRAP was also used to select the ions of interest for identification at a post-trap decay spectroscopy station. A new beta-decaying high-spin isomer feeding the 15− isomer in $^{128}$Sn has been discovered in $^{128}$In at 1797.6(20) keV. Shell-model calculations employing a CD-Bonn potential re-normalized with the perturbative G-matrix approach suggest this new isomer to be a 16+ spin-trap isomer. In …

Direct determination of the atomic mass difference of the pairs As76−Se76 and Tb155−Gd155 rules out As76 and Tb155 as possible candidates for electron (anti)neutrino mass measurements

Direct measurement of the mass difference of As 72 − Ge 72 rules out As 72 as a promising β -decay candidate to determine the neutrino mass

Evolution of Octupole Deformation in Radium Nuclei from Coulomb Excitation of Radioactive Ra222 and Ra228 Beams

There is sparse direct experimental evidence that atomic nuclei can exhibit stable "pear" shapes arising from strong octupole correlations. In order to investigate the nature of octupole collectivity in radium isotopes, electric octupole (E3) matrix elements have been determined for transitions in ^{222,228}Ra nuclei using the method of sub-barrier, multistep Coulomb excitation. Beams of the radioactive radium isotopes were provided by the HIE-ISOLDE facility at CERN. The observed pattern of E3 matrix elements for different nuclear transitions is explained by describing ^{222}Ra as pear shaped with stable octupole deformation, while ^{228}Ra behaves like an octupole vibrator.

Direct measurement of the mass difference of As72−Ge72 rules out As72 as a promising β -decay candidate to determine the neutrino mass

We report the first direct determination of the ground-state to ground-state electron-capture $Q$ value for the $^{72}\mathrm{As}$ to $^{72}\mathrm{Ge}$ decay by measuring their atomic mass difference utilizing the double Penning trap mass spectrometer, JYFLTRAP. The $Q$ value was measured to be 4343.596(75) keV, which is more than a fiftyfold improvement in precision compared to the value in the most recent Atomic Mass Evaluation 2020. Furthermore, the new $Q$ value was found to be 12.4(40) keV (3.1 $\ensuremath{\sigma}$) lower. With the significant reduction of the uncertainty of the ground-state to ground-state $Q$ value combined with the level scheme of $^{72}\mathrm{Ge}$ from $\ensurem…

Coulomb excitation of 222Rn

International audience; The nature of quadrupole and octupole collectivity in $^{222}$Rn was investigated by determining the electric-quadrupole (E2) and octupole (E3) matrix elements using subbarrier, multistep Coulomb excitation. The radioactive $^{222}$Rn beam, accelerated to 4.23 MeV/u, was provided by the HIE-ISOLDE facility at CERN. Data were collected in the Miniball $\gamma$ -ray spectrometer following the bombardment of two targets, $^{120}$Sn and $^{60}$Ni. Transition E2 matrix elements within the ground-state and octupole bands were measured up to 10 ¯h and the results were consistent with a constant intrinsic electric-quadrupole moment, 518(11) $e$ fm$^2$ . The values of the int…

The observation of vibrating pear-shapes in radon nuclei

6 pags., 4 fig.s, 1 tab. -- Open Access funded by Creative Commons Atribution Licence 4.0

Dy159 Electron-Capture: A New Candidate for Neutrino Mass Determination

Coulomb excitation of pear-shaped nuclei

There is a large body of evidence that atomic nuclei can undergo octupole distortion and assume the shape of a pear. This phenomenon is important for measurements of electric-dipole moments of atoms, which would indicate CP violation and hence probe physics beyond the Standard Model of particle physics. Isotopes of both radon and radium have been identified as candidates for such measurements. Here, we have observed the low-lying quantum states in 224Rn and 226Rn by accelerating beams of these radioactive nuclei. We show that radon isotopes undergo octupole vibrations but do not possess static pear-shapes in their ground states. We conclude that radon atoms provide less favourable condition…