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Abstract: The core-excited isomer in fully-ionized 133Sb has been directly studied for the first time by applying the novel technique of isochronous mass spectrometry at GSI. The neutron-rich nuclides in high charge states were produced by projectile fission of 411 MeV A 238U ions, separated in flight by the fragment separator (FRS) and stored in the isochronous storage ring (ESR). The measured excitation energy is 4.56(10) MeV. The neutral-atom half-life is known to be 17 μs. This is the shortest-lived isomer measured directly with mass spectrometry techniques. The extended in-flight half-life of the bare ions in the ESR, which is due to the exclusion of the strong internal conversion, demonstrates that there should be another nuclear level above that identified from isomer-decay spectroscopy, in support of shell-model calculations. This measurement opens up a new half-life domain for storage-ring measurements. [Copyright &y& Elsevier]

Mass measurements of exotic nuclei is a fast developing field which is essential for basic nuclear physics and a wide range of applications. The method of storage ring mass spectrometry has many advantages: (1) a large amount of nuclides can be simultaneously measured; (2) very short-lived (T1/2 ≳ 50 µs) and very rare species (yields down to single ions) can be accessed; (3) nuclides in several atomic charge states can be investigated; (4) half-life measurements can be performed with time-resolved mass spectrometry. In this contribution we concentrate on some recent achievements and future perspectives of the storage ring mass spectrometry. [ABSTRACT FROM AUTHOR]

For the first time the electron capture and β+ decay rates of H-like 140Pr ions have been measured at the FRS-ESR facility by using the Schottky noise technique. The H-like 140Pr58+ decay rate was found to be larger by a factor of 1.5 than in the case of neutral atom. This non-intuitive result can be explained by taking into account hyperfine splitting of nuclear levels in the decaying nuclei and the conservation law of the total angular momentum of the system. [ABSTRACT FROM AUTHOR]

The FRS-ESR facility at GSI provides one of the most efficient methods for direct mass measurements. In the present experiment, exotic nuclei were produced via fragmentation of 152Sm projectiles in a thick beryllium target at 500-600 MeV/u, separated in-flight with the fragment separator FRS, and injected into the storage-cooler ring ESR. Time-resolved Schottky Mass Spectrometry was applied for mass measurements of stored and electron-cooled bare and few-electron ions. 373 different nuclides were identified by means of the spectra of their revolution frequencies. Masses for 18 nuclides (84Zr, 92Ru, 94Rh, 107,108,110Sb, 111,112,114I, 118Ba, 122,123La, 124Ce, 127Pr, 129Nd, 132Pm, 134Sm, 137Eu) have been determined for the first time. Masses for 111,112I and 113Xe have been obtained via known α-decay energies. The experiment and first results will be presented. [ABSTRACT FROM AUTHOR]

A new long-lived isomeric state in the near proton dripline nucleus 125Ce has been identified with Schottky mass spectrometry at GSI. The excitation energy E * = 103(12)keV and the decay time of 193(1)s have been obtained from a single stored fully ionized 125 m Ce58+ ion. The data implies an E3 transition and a 1/2+ assignment for the spin of the isomer. [ABSTRACT FROM AUTHOR]

Previously unknown isotopes 30Ar and 29C1 have been identified by measurement of the trajectories of their in-flight decay products 28S + p + p and 28S + p, respectively. The analysis of angular correlations of the fragments provided information on decay energies and the structure of the parent states. The ground states of 30Ar and 29C1 were found at 2.25-0.10+0.15 and 1.8 ±0.1 MeV above the two- and one-proton thresholds, respectively. The lowest states in 30Ar and 29C1 point to a violation of isobaric symmetry in the structure of these unbound nuclei. The two-proton decay has been identified in a transition region between simultaneous two-proton and sequential proton emissions from the 30Ar ground state, which is characterized by an interplay of three-body and two-body decay mechanisms. The first hint of a fine structure of the two-proton decay of 30Ar* (2+) has been obtained by detecting two decay branches into the ground and first-excited states of the 28S fragment. [ABSTRACT FROM AUTHOR]

The first determination of radii of point proton distribution (proton radii) of B12-17 from charge-changing cross sections (σCC) measurements at the FRS, GSI, Darmstadt is reported. The proton radii are deduced from a finite-range Glauber model analysis of the σCC. The radii show an increase from 13B to 17B and are consistent with predictions from the antisymmetrized molecular dynamics model for the neutron-rich nuclei. The measurements show the existence of a thick neutron surface with neutron-proton radius difference of 0.51(0.11) fm in B. [ABSTRACT FROM AUTHOR]

The one-neutron removal cross sections of neutron-rich Al isotopes and longitudinal momentum distributions of the residues have been measured for A = 33 to 36 at relativistic energies (≈900 MeV/u). The inclusive data have been interpreted within the eikonal approximation. The evolution of the single-particle occupancy in the ground state of 33,34,35A1 has been studied and compared with shell model predictions. The inferred 2s1/2 neutron occupancy in the 33A1 ground-state wave function is 20% to 40% lower than the predicted one. The inclusive data do not exclude the presence of intruder states. Some intruder / = 1 occupancy is found in 34A1, similarly to 33Mg. The single-particle 1 f7/2 occupancy shows a gradual increase at N = 22. Correspondingly, a decrease of the lrf3/2 strength has been observed. [ABSTRACT FROM AUTHOR]

The interaction cross sections of 32-35Mg at 900A MeV have been measurmed using the fragment separator at GSI. The deviation from the r0A1/3 trend is slightly larger for 35Mg, signaling the possible formation of a longer tail in the neutron distribution for 35Mg. The radii extracted from a Glauber model analysis with Fermi densities are consistent with models predicting the development of neutron skins. [ABSTRACT FROM AUTHOR]

Abstract: The and orbital electron-capture decays of stored hydrogen- and helium-like 142Pm ions have been measured. So far, such measurements have been performed with only one nucleus, namely 140Pr. The electron-capture decay constant of hydrogen-like 142Pm60+ ions is about 50% larger than that of helium-like 142Pm59+ ions, which is in excellent agreement with the previous measurements in 140Pr ions and with new theoretical predictions. [Copyright &y& Elsevier]

We report the charge-changing cross sections (σ cc ) of 24 p-shell nuclides on both hydrogen and carbon at about 900A MeV, of which 8,9 Li, 10-12 Be, 10,14,15 B, 14,15,17-22 N and 16 O on hydrogen and 8,9 Li on carbon are for the first time. Benefiting from the data set, we found a new and robust relationship between the scaling factor of the Glauber model calculations and the separation energies of the nuclei of interest on both targets. This allows us to deduce proton radii (R p ) for the first time from the cross sections on hydrogen. Nearly identical R p values are deduced from both target data for the neutron-rich carbon isotopes; however, the R p from the hydrogen target is systematically smaller in the neutron-rich nitrogen isotopes. This calls for further experimental and theoretical investigations., (Copyright © 2024 Science China Press. Published by Elsevier B.V. All rights reserved.)

The first measurement of the momentum distribution for one-neutron removal from (24)O at 920A MeV performed at GSI, Darmstadt is reported. The observed distribution has a width (FWHM) of 99 +/- 4 MeV/c in the projectile rest frame and a one-neutron removal cross section of 63 +/- 7 mb. The results are well explained with a nearly pure 2s_{1/2} neutron spectroscopic factor of 1.74 +/- 0.19 within the eikonal model. This large s-wave probability shows a spherical shell closure thereby confirming earlier suggestions that (24)O is a new doubly magic nucleus.

Time-resolved Schottky mass spectrometry has been applied to uranium projectile fragments which yielded the mass value for the 208Hg (Z=80, N=128) isotope. The mass excess value of ME=-13 265(31) keV has been obtained, which has been used to determine the proton-neutron interaction strength in 210Pb, as a double difference of atomic masses. The results show a dramatic variation of the strength for lead isotopes when crossing the N=126 neutron shell closure, thus confirming the empirical predictions that this interaction strength is sensitive to the overlap of the wave functions of the last valence neutrons and protons.