Proton Shell Gaps in N=28 Nuclei from the First Complete Spectroscopy Study with FRIB Decay Station Initiator.

The first complete measurement of the ß-decay strength distribution of _{17}^{45}Cl_{28} was performed at the Facility for Rare Isotope Beams (FRIB) with the FRIB Decay Station Initiator during the second FRIB experiment. The measurement involved the detection of neutrons and γ rays in two focal planes of the FRIB Decay Station Initiator in a single experiment for the first time. This enabled an analytical consistency in extracting the ß-decay strength distribution over the large range of excitation energies, including neutron unbound states. We observe a rapid increase in the ß-decay strength distribution above the neutron separation energy in _{18}^{45}Ar_{27}. This was interpreted to be caused by the transitioning of neutrons into protons excited across the Z=20 shell gap. The SDPF-MU interaction with reduced shell gap best reproduced the data. The measurement demonstrates a new approach that is sensitive to the proton shell gap in neutron rich nuclei according to SDPF-MU calculations.

Microsecond Isomer at the N=20 Island of Shape Inversion Observed at FRIB.

Excited-state spectroscopy from the first experiment at the Facility for Rare Isotope Beams (FRIB) is reported. A 24(2)-µs isomer was observed with the FRIB Decay Station initiator (FDSi) through a cascade of 224- and 401-keV γ rays in coincidence with ^{32}Na nuclei. This is the only known microsecond isomer (1 µs≤T_{1/2}<1 ms) in the region. This nucleus is at the heart of the N=20 island of shape inversion and is at the crossroads of the spherical shell-model, deformed shell-model, and ab initio theories. It can be represented as the coupling of a proton hole and neutron particle to ^{32}Mg, ^{32}Mg+π^{-1}+ν^{+1}. This odd-odd coupling and isomer formation provides a sensitive measure of the underlying shape degrees of freedom of ^{32}Mg, where the onset of spherical-to-deformed shape inversion begins with a low-lying deformed 2^{+} state at 885 keV and a low-lying shape-coexisting 0_{2}^{+} state at 1058 keV. We suggest two possible explanations for the 625-keV isomer in ^{32}Na: a 6^{-} spherical shape isomer that decays by E2 or a 0^{+} deformed spin isomer that decays by M2. The present results and calculations are most consistent with the latter, indicating that the low-lying states are dominated by deformation.

Crossing N=28 Toward the Neutron Drip Line: First Measurement of Half-Lives at FRIB.

New half-lives for exotic isotopes approaching the neutron drip-line in the vicinity of N∼28 for Z=12-15 were measured at the Facility for Rare Isotope Beams (FRIB) with the FRIB decay station initiator. The first experimental results are compared to the latest quasiparticle random phase approximation and shell-model calculations. Overall, the measured half-lives are consistent with the available theoretical descriptions and suggest a well-developed region of deformation below ^{48}Ca in the N=28 isotones. The erosion of the Z=14 subshell closure in Si is experimentally confirmed at N=28, and a reduction in the ^{38}Mg half-life is observed as compared with its isotopic neighbors, which does not seem to be predicted well based on the decay energy and deformation trends. This highlights the need for both additional data in this very exotic region, and for more advanced theoretical efforts.

Competition between Allowed and First-Forbidden ß Decay: The Case of

The ß decay of ^{208}Hg into the one-proton hole, one neutron-particle _{81}^{208}Tl_{127} nucleus was investigated at CERN-ISOLDE. Shell-model calculations describe well the level scheme deduced, validating the proton-neutron interactions used, with implications for the whole of the N>126, Z<82 quadrant of neutron-rich nuclei. While both negative and positive parity states with spin 0 and 1 are expected within the Q_{ß} window, only three negative parity states are populated directly in the ß decay. The data provide a unique test of the competition between allowed Gamow-Teller and Fermi, and first-forbidden ß decays, essential for the understanding of the nucleosynthesis of heavy nuclei in the rapid neutron capture process. Furthermore, the observation of the parity changing 0^{+}→0^{-}ß decay where the daughter state is core excited is unique, and can provide information on mesonic corrections of effective operators.

Publisher's Note: Direct Lifetime Measurements of the Excited States in

This corrects the article DOI: 10.1103/PhysRevLett.116.122502.

First Accurate Normalization of the ß-delayed α Decay of

The ^{12}C(α,γ)^{16}O reaction plays a central role in astrophysics, but its cross section at energies relevant for astrophysical applications is only poorly constrained by laboratory data. The reduced α width, γ_{11}, of the bound 1^{-} level in ^{16}O is particularly important to determine the cross section. The magnitude of γ_{11} is determined via sub-Coulomb α-transfer reactions or the ß-delayed α decay of ^{16}N, but the latter approach is presently hampered by the lack of sufficiently precise data on the ß-decay branching ratios. Here we report improved branching ratios for the bound 1^{-} level [b_{ß,11}=(5.02±0.10)×10^{-2}] and for ß-delayed α emission [b_{ßα}=(1.59±0.06)×10^{-5}]. Our value for b_{ßα} is 33% larger than previously held, leading to a substantial increase in γ_{11}. Our revised value for γ_{11} is in good agreement with the value obtained in α-transfer studies and the weighted average of the two gives a robust and precise determination of γ_{11}, which provides significantly improved constraints on the ^{12}C(α,γ) cross section in the energy range relevant to hydrostatic He burning.

Impact of Modular Total Absorption Spectrometer measurements of ß decay of fission products on the decay heat and reactor ν[over ¯]_{e} flux calculation.

We report the results of a ß-decay study of fission products ^{86}Br, ^{89}Kr, ^{89}Rb, ^{90gs}Rb, ^{90m}Rb, ^{90}Kr, ^{92}Rb, ^{139}Xe, and ^{142}Cs performed with the Modular Total Absorption Spectrometer (MTAS) and on-line mass-separated ion beams. These radioactivities were assessed by the Nuclear Energy Agency as having high priority for decay heat analysis during a nuclear fuel cycle. We observe a substantial increase in ß feeding to high excited states in all daughter isotopes in comparison to earlier data. This increases the average γ-ray energy emitted by the decay of fission fragments during the first 10 000 s after fission of ^{235}U and ^{239}Pu by approximately 2% and 1%, respectively, improving agreement between results of calculations and direct observations. New MTAS results reduce the reference reactor ν[over ¯]_{e} flux used to analyze reactor ν[over ¯]_{e} interaction with detector matter. The reduction determined by the ab initio method for the four nuclear fuel components, ^{235}U, ^{238}U, ^{239}Pu, and ^{241}Pu, amounts to 0.976, 0.986, 0.983, and 0.984, respectively.

Evidence for Gamow-Teller Decay of

The ß-delayed neutron emission of ^{83,84}Ga isotopes was studied using the neutron time-of-flight technique. The measured neutron energy spectra showed emission from states at excitation energies high above the neutron separation energy and previously not observed in the ß decay of midmass nuclei. The large decay strength deduced from the observed intense neutron emission is a signature of Gamow-Teller transformation. This observation was interpreted as evidence for allowed ß decay to ^{78}Ni core-excited states in ^{83,84}Ge favored by shell effects. We developed shell model calculations in the proton fpg_{9/2} and neutron extended fpg_{9/2}+d_{5/2} valence space using realistic interactions that were used to understand measured ß-decay lifetimes. We conclude that enhanced, concentrated ß-decay strength for neutron-unbound states may be common for very neutron-rich nuclei. This leads to intense ß-delayed high-energy neutron and strong multineutron emission probabilities that in turn affect astrophysical nucleosynthesis models.

Direct Lifetime Measurements of the Excited States in (72)Ni.

The lifetimes of the first excited 2^{+} and 4^{+} states in ^{72}Ni were measured at the National Superconducting Cyclotron Laboratory with the recoil-distance Doppler-shift method, a model-independent probe to obtain the reduced transition probability. Excited states in ^{72}Ni were populated by the one-proton knockout reaction of an intermediate energy ^{73}Cu beam. γ-ray-recoil coincidences were detected with the γ-ray tracking array GRETINA and the S800 spectrograph. Our results provide evidence of enhanced transition probability B(E2;2^{+}→0^{+}) as compared to ^{68}Ni, but do not confirm the trend of large B(E2) values reported in the neighboring isotope ^{70}Ni obtained from Coulomb excitation measurement. The results are compared to shell model calculations. The lifetime obtained for the excited 4_{1}^{+} state is consistent with models showing decay of a seniority ν=4, 4^{+} state, which is consistent with the disappearance of the 8^{+} isomer in ^{72}Ni.

Large ß-delayed one and two neutron emission rates in the decay of 86Ga.

Beta decay of 86Ga was studied by means of ß-neutron-γ spectroscopy. An isotopically pure ^{86}Ga beam was produced at the Holifield Radioactive Ion Beam Facility using a resonance ionization laser ion source and high-resolution electromagnetic separation. The decay of 86Ga revealed a half-life of 43(-15)(+21) ms and large ß-delayed one-neutron and two-neutron branching ratios of P1n=60(10)% and P2n=20(10)%. The ßγ decay of 86Ga populated a 527 keV transition that is interpreted as the deexcitation of the first 2+ state in the N=54 isotone 86Ge and suggests a quick onset of deformation in Ge isotopes beyond N=50.

11Li Breakup on 208 at energies around the Coulomb barrier.

The inclusive breakup for the (11)Li + (208)Pb reaction at energies around the Coulomb barrier has been measured for the first time. A sizable yield of (9)Li following the (11)Li dissociation has been observed, even at energies well below the Coulomb barrier. Using the first-order semiclassical perturbation theory of Coulomb excitation it is shown that the breakup probability data measured at small angles can be used to extract effective breakup energy as well as the slope of B(E1) distribution close to the threshold. Four-body continuum-discretized coupled-channels calculations, including both nuclear and Coulomb couplings between the target and projectile to all orders, reproduce the measured inclusive breakup cross sections and support the presence of a dipole resonance in the (11)Li continuum at low excitation energy.

New half-lives of r-process Zn and Ga isotopes measured with electromagnetic separation.

The ß decays of neutron-rich nuclei near the doubly magic (78)Ni were studied at the Holifield Radioactive Ion Beam Facility using an electromagnetic isobar separator. The half-lives of (82)Zn (228±10 ms), (83)Zn (117±20 ms), and (85)Ga (93±7 ms) were determined for the first time. These half-lives were found to be very different from the predictions of the global model used in astrophysical simulations. A new calculation was developed using the density functional model, which properly reproduced the new experimental values. The robustness of the new model in the (78)Ni region allowed us to extrapolate data for more neutron-rich isotopes. The revised analysis of the rapid neutron capture process in low entropy environments with our new set of measured and calculated half-lives shows a significant redistribution of predicted isobaric abundances strengthening the yield of A>140 nuclei.

Improved limit on direct α decay of the Hoyle state.

The current evaluation of the triple-α reaction rate assumes that the α decay of the 7.65 MeV, 0+ state in 12C, commonly known as the Hoyle state, proceeds sequentially via the ground state of 8Be. This assumption is challenged by the recent identification of two direct α-decay branches with a combined branching ratio of 17(5)%. If correct, this would imply a corresponding reduction in the triple-α reaction rate with important astrophysical consequences. We have used the 11B(3He,d) reaction to populate the Hoyle state and measured the decay to three α particles in complete kinematics. We find no evidence for direct α-decay branches, and hence our data do not support a revision of the triple-α reaction rate. We obtain an upper limit of 5×10(-3) on the direct α decay of the Hoyle state at 95% C.L., which is 1 order of magnitude better than a previous upper limit.

Do halo nuclei follow Rutherford elastic scattering at energies below the barrier? The case of 11Li.

The first measurement of the elastic scattering of the halo nucleus 11Li and its core 9Li on 208Pb at energies near the Coulomb barrier is presented. The 11Li+208Pb elastic scattering shows a strong reduction with respect to the Rutherford cross section, even at energies well below the barrier and down to very small scattering angles. This drastic change of the elastic differential cross section observed in 11Li+208Pb is the consequence of the halo structure of 11Li, as it is not observed in the elastic scattering of its core 9Li at the same energies. Four-body continuum-discretized coupled-channels calculations, based on a three-body model of the 11Li projectile, are found to explain the measured angular distributions and confirm that the observed reduction is mainly due to the strong Coulomb coupling to the dipole states in the low-lying continuum of 11Li. These calculations suggest the presence of a low-lying dipole resonance in 11Li close to the breakup threshold.

Increase of resistance to macrolides in invasive Streptococcus pneumoniae in Spain (2000-2001).

This study examined the antimicrobial resistance of 1,278 invasive Streptococcus pneumoniae isolates from 41 Spanish laboratories participating in the European Antimicrobial Resistance Surveillance System (EARSS) during 2000 and 2001. Twenty-nine laboratories participated during both years and provided 950 of the isolates. Each laboratory used its own susceptibility testing methods. External quality assessment was performed annually by each participating laboratory. Significant increases in penicillin and erythromycin resistance were observed between 2000 and 2001. This increase was particularly noticeable in isolates from the laboratories participating during both years and in isolates from children and elderly patients.

[Ticlopidine use in Spain: a pharmacy-based drug utilization study]. / Estudio de la utilización de ticlopidina en oficinas de farmacia de España.

BACKGROUND: In 1997 a program was set up to improve the use of ticlopidine. In the present study we assess whether this objective was achieved. PATIENTS AND METHODS: We carried out a pharmacy-based cross-sectional study. RESULTS: Out of 346 patients interviewed, 56% presented an off-label indication for ticlopidine. In 23% of patients the daily dose used was lower or higher than the recommended. Only 28% patients had the fortnightly blood monitoring performed at the time of interview. CONCLUSIONS: The use of ticlopidine in Spain is not consistent with the summary of product characteristics and the program set up to improve it did not achieve a satisfactory result.

[Safety of meningococcal A and C vaccine. Data from the Spanish drug surveillance system. Meningococcal Vaccine Research Group of the Spanish System of Drug Surveillance]. / Seguridad de la vacuna antimeningocócica A+C. Datos recogidos por el Sistema Español de Farmacovigilancia. Grupo de Investigación sobre la vacuna antimeningocócica del Sistema Español de Farmacogigilancia.

OBJECTIVE: Data on meningococcal vaccines safety are scanty. In 1997 several vaccination campaign took place in Spain. Thus, this situation was used to improve our knowledge about the safety profile of this vaccine. METHODS: An inquiry was carried out to the Regional Centers of the Spanish Pharmacovigilance System to know the number of vaccinated people and the type and number of suspected cases of adverse reactions. RESULTS: There were 133 identified cases of suspected adverse reactions associated with meningococcal A and C vaccine until June 1st, 1998. Most of them affected the skin (25,3%) or nervous system (similar proportion). Those of allergic reactions accounted for 35,2%. Two cases were considered as severe, although they were resolved without secuelae. CONCLUSIONS: Serious risks were not detected. The Spanish Pharmacosurveillance System as an epidemiological surveillance resource has been useful to know the safety problems associated with antimeningococcal vaccine in the community.

[Use of antihypertensive drugs in Spain, 1985-1995]. / Uso de antihipertensivos en España, 1985-1995.

BACKGROUND: This study has analysed the trend of antihypertensive drugs consumption in Spain from 1985 to 1995, its economical impact and the correlation with the available scientific evidence. The utilization of calcium channel blockers in the context of the recent controversial about their safety profile was also evaluated. METHODS: Drugs from the ATC groups C02, C03 (excluding C03C), C07, C08 (excluding nimodipine and nicardipine) and C09 were included (ATC classification, 1996 version). Drug utilization data and cost figures were obtained from the databases ECOM and FAR-90 of the Ministry of Health. These databases contain the number of packages sold in community pharmacies that are charged to the National Health System. Data are expressed in defined daily doses per 1,000 inhabitants per day (DHD). The cost is expressed in current and constant pesetas. RESULTS: The use of antihypertensives increased from 34.78 DHD in 1985 to 103.55 DHD in 1995. Angiotensin-converting enzyme inhibitors (ACEI) and calcium channel blockers (CCB) are responsible for 89% of the total increase. Thiazides and beta-blockers showed a mild increase, although its relative contribution to the total figures declined from 72 to 32% at the end of the period. Rauwolfia alcaloids and antiadrenergic drugs sales were negligible (0.4% of total sales in 1995). Within the thiazides, consumption was concentrated in products containing > or = 50 mg hydrochlorothiazide or equivalent. Enalapril, captopril, nifedipine and the fixed-dose association of hydrochlorothiazide with amiloride were the most widely used drugs. The cost of antihypertensive drugs in current pesetas raised eight times through the study period reaching 105,501 millions pesetas in 1995; 89% of the cost corresponded to ACEI and CCB. Expressed in constant pesetas the cost increase was four fold. The recent controversia about CCB did not have influence on its consumption. CONCLUSIONS: The pattern of use of antihypertensive drugs in Spain does not follow the available scientific evidence. Drugs with less documented effectiveness are the most prescribed; even considering the same effectiveness, efficiency is lower for drugs with higher utilization rates. The available presentations for thiazides makes their utilization in the optimal dosification difficult.