Ground-State g Factor of Highly Charged

A method is proposed to determine the M1 nuclear transition amplitude and hence the lifetime of the "nuclear clock transition" between the low-lying (∼8 eV) first isomeric state and the ground state of ^{229}Th from a measurement of the ground-state g factor of few-electron ^{229}Th ions. As a tool, the effect of nuclear hyperfine mixing in highly charged ^{229}Th ions such as ^{229}Th^{89+} or ^{229}Th^{87+} is used. The ground-state-only g-factor measurement would also provide first experimental evidence of nuclear hyperfine mixing in atomic ions. Combining the measurements for H-, Li-, and B-like ^{229}Th ions has a potential to improve the initial result for a single charge state and to determine the nuclear magnetic moment to a higher accuracy than that of the currently accepted value. The calculations include relativistic, interelectronic-interaction, QED, and nuclear effects.

Approaching the Gamow Window with Stored Ions: Direct Measurement of

We report the first measurement of low-energy proton-capture cross sections of ^{124}Xe in a heavy-ion storage ring. ^{124}Xe^{54+} ions of five different beam energies between 5.5 and 8 AMeV were stored to collide with a windowless hydrogen target. The ^{125}Cs reaction products were directly detected. The interaction energies are located on the high energy tail of the Gamow window for hot, explosive scenarios such as supernovae and x-ray binaries. The results serve as an important test of predicted astrophysical reaction rates in this mass range. Good agreement in the prediction of the astrophysically important proton width at low energy is found, with only a 30% difference between measurement and theory. Larger deviations are found above the neutron emission threshold, where also neutron and γ widths significantly impact the cross sections. The newly established experimental method is a very powerful tool to investigate nuclear reactions on rare ion beams at low center-of-mass energies.

Observation of coherence in the time-reversed relativistic photoelectric effect.

The photoelectric effect has been studied in the regime of hard x rays and strong Coulomb fields via its time-reversed process of radiative recombination (RR). In the experiment, the relativistic electrons recombined into the 2p_{3/2} excited state of hydrogenlike uranium ions, and both the RR x rays and the subsequently emitted characteristic x rays were detected in coincidence. This allowed us to observe the coherence between the magnetic substates in a highly charged ion and to identify the contribution of the spin-orbit interaction to the RR process.

Discovery of highly excited long-lived isomers in neutron-rich hafnium and tantalum isotopes through direct mass measurements.

A study of cooled ¹97Au projectile-fragmentation products has been performed with a storage ring. This has enabled metastable nuclear excitations with energies up to 3 MeV, and half-lives extending to minutes or longer, to be identified in the neutron-rich nuclides ¹8³(,)¹84(,)¹86Hf and ¹86(,)¹87Ta. The results support the prediction of a strongly favored isomer region near neutron number 116.

Direct determination of the magnetic quadrupole contribution to the Lyman-α1 transition in a hydrogenlike ion.

We report the observation of an interference between the electric dipole (E1) and the magnetic quadrupole (M2) amplitudes for the linear polarization of the Ly-α1 (2p3/2→1s1/2) radiation of hydrogenlike uranium. This multipole mixing arises from the coupling of the ion to different multipole components of the radiation field. Our observation indicates a significant depolarization of the Ly-α1 radiation due to the E1-M2 amplitude mixing. It proves that a combined measurement of the linear polarization and of the angular distribution enables a very precise determination of the ratio of the E1 and the M2 transition amplitudes and the corresponding transition rates without any assumptions concerning the population mechanism for the 2p3/2 state.

Isotope shift in the dielectronic recombination of three-electron ANd57+.

Isotope shifts in dielectronic recombination spectra were studied for Li-like (A)Nd(57+) ions with A=142 and A=150. From the displacement of resonance positions energy shifts deltaE(142 150)(2s-2p(1/2))=40.2(3)(6) meV [(stat)(sys)] and deltaE(142 150)(2s-2p(3/2))=42.3(12)(20) meV of 2s-2p(j) transitions were deduced. An evaluation of these values within a full QED treatment yields a change in the mean-square charge radius of (142 150)deltar(2)=-1.36(1)(3) fm(2). The approach is conceptually new and combines the advantage of a simple atomic structure with high sensitivity to nuclear size.

Screened radiative corrections from hyperfine-split dielectronic resonances in lithiumlike scandium.

Term energies for dielectronic-recombination Rydberg resonances below 0.07 eV are determined for Sc18+ with absolute accuracies below 0.0002 eV by electron collision spectroscopy in an ion storage ring, using the twin-electron-beam technique and a cryogenic photocathode. The lithiumlike 2s_{1/2}-2p_{3/2} transition energy for Z=21 is determined to 4.6 ppm, less than 1% of the few-body effects on radiative corrections. Features from the hyperfine structure of the 2s state could be resolved in the dielectronic-recombination spectrum.

Measurement of the beta+ and orbital electron-capture decay rates in fully ionized, hydrogenlike, and heliumlike 140Pr ions.

We report on the first measurement of the beta+ and orbital electron-capture decay rates of 140Pr nuclei with the simplest electron configurations: bare nuclei, hydrogenlike, and heliumlike ions. The measured electron-capture decay constant of hydrogenlike 140Pr58+ ions is about 50% larger than that of heliumlike 140Pr57+ ions. Moreover, 140Pr ions with one bound electron decay faster than neutral 140Pr0+ atoms with 59 electrons. To explain this peculiar observation one has to take into account the conservation of the total angular momentum, since only particular spin orientations of the nucleus and of the captured electron can contribute to the allowed decay.

Precise determination of the 2s(1/2)-2p(1/2) splitting in very heavy lithiumlike ions utilizing dielectronic recombination.

The 2s(1/2)-2p(1/2) energy splittings DeltaE(L) of the lithiumlike ions 19779Au76+, 20882Pb79+, and 23892U89+ have been measured at the Experimental Storage Ring, utilizing low energy dielectronic recombination. The resonance energies in total 41 different 1s(2) 2p(1/2)nl(j(')) (n > or =20) autoionizing Rydberg states populated in the dielectronic capture process have been determined. The 2s(1/2)-->2p(1/2) excitation energies have been obtained by extrapolation of these resonance energies to the associated series limits n--> infinity. The combined analysis of the experimental data for all three ions yields DeltaE(L)=216.134(96) eV for Au76+, 230.650(81) eV for Pb79+, and 280.516(99) eV for U89+.

High Rydberg resonances in dielectronic recombination of pb(79+).

Dielectronic recombination resonances of Pb (79+) associated with 2s(1/2)-->2p(1/2) excitations were measured at the heavy-ion storage ring ESR at GSI. The fine structure of the energetically lowest resonance manifold Pb (78+)(1s(2)2p(1/2)20l(j)) at around 18 eV could partially be resolved, and rate coefficients on an absolute scale were obtained. A comparison of the experimental data with results of a fully relativistic theoretical approach shows that high-angular-momentum components up to j=31/2 significantly contribute to the total resonance strength demonstrating the necessity to revise the widespread notion of negligible high-angular-momentum contributions at least for very highly charged ions.

Triggers of overeating and related intervention strategies for women who weight cycle.

The purpose of this study was to describe overeating episodes of overweight women who weight cycle compared with women of normal weight. Repeated overeating can be a major source of excess calories that may lead to weight gain in women who have weight cycled. Interview transcripts about overeating episodes of 45 women were subjected to a content analysis in a qualitative secondary analysis of data. Four patterns emerged from the data: planned overeating, power/control, relationships with others, and unpleasant feelings. Three intervention strategies are described to assist women who have weight cycled to understand and deal with feelings that trigger overeating, including strategies to stop overeating, feel their feelings, and fight fairly.

Immunocytochemical identification of a bovine peritoneal mesothelioma.

Peritoneal mesotheliomas are uncommon among cows although there has been an increase in the frequency of diagnosis of this neoplasia in the past few years. The case of a 2 year old cow is described. On post-mortem examination, several nodules of variable size were found in the peritoneal cavity. These nodules fused together, but they did not go deep into the organs. Histologically, such nodules were formed by a population of fusiform cells of malignant morphological character and sarcomatous appearance. Immunocytochemical study, using P.A.P. techniques, showed a highly positive reaction towards vimentin and a negative reaction towards wide-spectrum cytokeratins, hence suggesting a mesenchymal origin of the neoplasia. According to the histopathological study, a multifocal peritoneal mesothelioma of sarcomatous appearance was identified.