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An evident odd-even staggering (OES) in fragment cross sections has been experimentally observed in many fragmentation and spallation reactions. However, quantitative comparisons of this OES effect in different reaction systems are still scarce for neutron-rich nuclei near the neutron drip line. By employing a third-order difference formula, the magnitudes of this OES in extensive experimental cross sections are systematically investigated for many neutron-rich nuclei with (N-Z) from 1 to 23 over a broad range of atomic numbers (Z≈3-50). A comparison of these magnitude values extracted from fragment cross sections measured in different fragmentation and spallation reactions with a large variety of projectile-target combinations over a wide energy range reveals that the OES magnitude is almost independent of the projectile-target combinations and the projectile energy. The weighted average of these OES magnitudes derived from cross sections accurately measured in different reaction systems is adopted as the evaluation value of the OES magnitude. These evaluated OES magnitudes are recommended to be used in fragmentation and spallation models to improve their predictions for fragment cross sections. [ABSTRACT FROM AUTHOR]

Lifetime measurements of α-decaying highly charged ions have been performed in the experimental storage ring (CSRe) by applying the isochronous Schottky mass spectrometry. The fully ionized 49Cr and 53Fe ions were produced in projectile fragmentation of 58Ni primary beam and were stored in the CSRe tuned into the isochronous ion-optical mode. The new resonant Schottky detector was applied to monitor the intensities of stored uncooled 49Cr24+ and 53Fe26+ ions. The extracted half-lives T1/2(49Cr24+)=44.0(27) min and T1/2(53Fe26+)=8.47(19) min are in excellent agreement with the literature half-life values corrected for the disabled electron capture branchings. This is an important proof-of-principle step towards realizing the simultaneous mass and lifetime measurements on exotic nuclei at the future storage ring facilities. [ABSTRACT FROM AUTHOR]

Isochronous mass spectrometry was applied to measure isomeric yield ratios of fragmentation reaction products. This approach is complementary to conventional γ-ray spectroscopy in particular for measuring yield ratios for long-lived isomeric states. Isomeric yield ratios for the high-spin I=19/2ℏ states in the mirror nuclei 53Fe and 53Co are measured to study angular momentum population following the projectile fragmentation of 78Kr at energies of ~480A MeV on a beryllium target. The 19/2 state isomeric ratios of 53Fe produced from different projectiles in the literature have also been extracted as a function of mass number difference between projectile and fragment (mass loss). The results are compared to ABRABLA07 model calculations. The isomeric ratios of 53Fe produced using different projectiles suggest that the theory underestimates not only the previously reported dependence on the spin but also the dependence on the mass loss. [ABSTRACT FROM AUTHOR]

Strong odd-even staggering (OES) of the yields of fragments, produced by fragmenting 78Kr projectiles, has been measured by employing the combination of an in-flight fragment separator and a storage ring. It is shown that the OES of fragment yields of Tz=-1/2 and Tz=1/2 mirror nuclei critically depends on both pairing and shell structure, especially at the closed shells Z = 20 and 28. A comparison of the relative OES of yields and of particle-emission threshold energies reveals unambiguously that the origin of the OES of fragment yields is mainly determined by the OES of the particle-emission threshold energies, which contain both pairing and shell effects. [ABSTRACT FROM AUTHOR]

The very first in-ring reaction experiment at the Cooler Storage Ring at the Heavy Ion Research Facility in Lanzhou (HIRFL-CSR), namely proton elastic scattering on stable 58Ni nuclei, is presented. The circulating 58Ni19+ ions with an energy of 95 MeV/u were interacting repeatedly with an internal hydrogen gas target in the experimental storage ring (CSRe). Low-energy proton recoils from the elastic collisions were measured with an ultra-high vacuum compatible silicon-strip detector. Deduced differential cross sections were normalized by measuring k-shell x rays from 58Ni19+ projectiles due to the 58Ni19+-H2 ionization collisions. Compared to the experimental cross sections, a good agreement has been achieved with the theoretical predictions in the measured region, which were obtained by using the global phenomenological optical model potentials. Our results enable new research opportunities for optical model potential studies on exotic nuclides by using the in-ring reaction setup at the HIRFL-CSR facility. [ABSTRACT FROM AUTHOR]

The longitudinal momentum distributions of 7Be fragments in the breakup of 8B on a carbon target have been measured at 36 MeV/u. The different mechanisms have been distinguished by coincidence measurements. The longitudinal momentum distributions of 7Be fragments from both the stripping and the diffraction mechanisms are consistent with the results of noneikonal calculations and CDCC calculations. The full widths at half maximum of the longitudinal momentum distributions are 124 ± 17 and 92 ± 7 MeV/c for the stripping and diffraction components, respectively. The comparison with the different model calculations is discussed. It is crucial to separate the different reaction mechanisms experimentally to benchmark nuclear reaction theories. [ABSTRACT FROM AUTHOR]

Isochronous mass spectrometry has been applied to neutron-deficient 58Ni projectile fragments at the HIRFL-CSR facility in Lanzhou, China. Masses of a series of short-lived Tz = -3/2 nuclides including 41Ti, 45Cr, 49Fe, and 53Ni have been measured with a precision of 20-40 keV. The new data enable us to test for the first time the isobaric multiplet mass equation (IMME) in fp-shell nuclei. We observe that the IMME is inconsistent with the generally accepted quadratic form for the A - 53, T = 3/2 quartet. We perform full space shell model calculations and compare them with the new experimental results. [ABSTRACT FROM AUTHOR]

Two generic methods based on frequentism and Bayesianism are presented in this work aiming to adequately estimate decay lifetimes from measured data, while accounting for restricted observation times in the measurements. All the experimental scenarios that can possibly arise from the observation constraints are treated systematically and formulas are derived. The methods are then tested against the decay data of bare isomeric 94mRu44+, which were measured using isochronous mass spectrometry with a timing detector at the CSRe in Lanzhou, China. Applying both methods in three distinct scenarios yields six different but consistent lifetime estimates. The deduced values are all in good agreement with a prediction based on the neutral-atom value modified to take the absence of internal conversion into account. Potential applications of such methods are discussed. [ABSTRACT FROM AUTHOR]

Masses of 52g,52mCo were measured for the first time with an accuracy of ~10 keV, an unprecedented precision reached for short-lived nuclei in the isochronous mass spectrometry. Combining our results with the previous β−γ measurements of 52Ni, the T=2, Jπ=0+ isobaric analog state (IAS) in 52Co was newly assigned, questioning the conventional identification of IASs from the β-delayed proton emissions. Using our energy of the IAS in 52Co, the masses of the T=2 multiplet fit well into the isobaric multiplet mass equation. We find that the IAS in 52Co decays predominantly via γ transitions while the proton emission is negligibly small. According to our large-scale shell model calculations, this phenomenon has been interpreted to be due to very low isospin mixing in the IAS. [ABSTRACT FROM AUTHOR]

Masses of ^{52g,52m}Co were measured for the first time with an accuracy of ∼10  keV, an unprecedented precision reached for short-lived nuclei in the isochronous mass spectrometry. Combining our results with the previous β-γ measurements of ^{52}Ni, the T=2, J^{π}=0^{+} isobaric analog state (IAS) in ^{52}Co was newly assigned, questioning the conventional identification of IASs from the β-delayed proton emissions. Using our energy of the IAS in ^{52}Co, the masses of the T=2 multiplet fit well into the isobaric multiplet mass equation. We find that the IAS in ^{52}Co decays predominantly via γ transitions while the proton emission is negligibly small. According to our large-scale shell model calculations, this phenomenon has been interpreted to be due to very low isospin mixing in the IAS.

Isochronous mass spectrometry has been applied to neutron-deficient 58Ni projectile fragments at the HIRFL-CSR facility in Lanzhou, China. Masses of a series of short-lived T(z)=-3/2 nuclides including 41Ti, 45Cr, 49Fe, and 53Ni have been measured with a precision of 20-40 keV. The new data enable us to test for the first time the isobaric multiplet mass equation (IMME) in fp-shell nuclei. We observe that the IMME is inconsistent with the generally accepted quadratic form for the A=53, T=3/2 quartet. We perform full space shell model calculations and compare them with the new experimental results.

Mass excesses of short-lived A=2Z-1 nuclei (63)Ge, (65)As, (67)Se, and (71)Kr have been directly measured to be -46,921(37), -46,937(85), -46,580(67), and -46,320(141)  keV, respectively. The deduced proton separation energy of -90(85)  keV for (65)As shows that this nucleus is only slightly proton unbound. X-ray burst model calculations with the new mass excess of (65)As suggest that the majority of the reaction flow passes through (64)Ge via proton capture, indicating that (64)Ge is not a significant rp-process waiting point.