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P Indelicato

Publications and source records attributed to P Indelicato.

At least 19 recordsLinked to original sources
PubMed2005

Dielectronic resonance method for measuring isotope shifts.

Long standing problems in the comparison of very accurate hyperfine-shift measurements to theory were partly overcome by precise measurements on few-electron highly charged ions. Still the agreement between theory and experiment is unsatisfactory. In this Letter, we present a radically new way of precisely measuring hyperfine shifts, and demonstrate its effectiveness in the case of the hyperfine shift of 4s1/2 and 4p1/2 in 207Pb53+. It is based on the precise detection of dielectronic resonances that occur in electron-ion recombination at very low energy. This allows us to determine the hyperfine constant to around 0.6 meV accuracy which is on the order of 10%.

Journal Article↗
PubMed2005

Nonrelativistic limit of Dirac-Fock codes: the role of Brillouin configurations.

We solve a long standing problem with relativistic calculations done with the widely used multiconfiguration Dirac-Fock method. We show, using relativistic many-body perturbation theory (RMBPT), how, even for relatively high-Z, relaxation or correlation causes the nonrelativistic limit of states of different total angular momentum but identical orbital angular momentum to have different energies. We show that only large scale calculations that include all single excitations, even those obeying Brillouin's theorem, have the correct limit. We reproduce very accurately recent high-precision measurements in F-like Ar, and turn then to a precise test of QED. We obtain the correct nonrelativistic limit not only for fine structure but also for level energies and show that RMBPT calculations are not immune to this problem.

Journal Article↗
PubMed2003

Low-energy X-ray standards from hydrogenlike pionic atoms.

We demonstrate the first step of a complete program, which consists in establishing an x-ray energy standard scale with the use of few-body atoms, in the few keV range. Light pionic and muonic atoms as well as one and two-electron ions from electron-cyclotron ion sources are used. The transition energies are calculable from quantum-electrodynamics, meaning that only a very limited subset need be measured and compared with theory, while providing a large number of standard lines. Here we show that circular transitions in pionic neon atoms, completely stripped from their electrons, reveal spectral lines which are narrow, symmetric, and well reproducible. We use these lines for the energy determination of transition energies in complex electronic systems, like the Kalpha(1,2) transitions in metallic Ti, which may serve as secondary standard.

Journal Article↗
PubMed2002

Self-energy correction to the bound-electron g factor in H-like ions.

The one-loop self-energy correction to the 1s-electron g factor is evaluated to all orders in Zalpha with an accuracy essentially better than that of previous calculations of this correction. As a result, the uncertainty of the theoretical prediction for the bound-electron g factor in H-like carbon is reduced by a factor of 3. This improves the total accuracy of the recent electron-mass determination [T. Beier, Phys. Rev. Lett. 88, 011603 (2002)]]. The new value of the electron mass is found to be m(e)=0.000 548 579 909 3 (3) u.

Journal Article↗
PubMed1999

Relationship between concussion and neuropsychological performance in college football players.

CONTEXT: Despite the high prevalence and potentially serious outcomes associated with concussion in athletes, there is little systematic research examining risk factors and short- and long-term outcomes. OBJECTIVES: To assess the relationship between concussion history and learning disability (LD) and the association of these variables with neuropsychological performance and to evaluate postconcussion recovery in a sample of college football players. DESIGN, SETTING, AND PARTICIPANTS: A total of 393 athletes from 4 university football programs across the United States received preseason baseline evaluations between May 1997 and February 1999. Subjects who had subsequent football-related acute concussions (n = 16) underwent neuropsychological comparison with matched control athletes from within the sample (n = 10). MAIN OUTCOME MEASURES: Clinical interview, 8 neuropsychological measures, and concussion symptom scale ratings at baseline and after concussion. RESULTS: Of the 393 players, 129 (34%) had experienced 1 previous concussion and 79 (20%) had experienced 2 or more concussions. Multivariate analysis of variance yielded significant main effects for both LD (P<.001) and concussion history (P=.009), resulting in lowered baseline neuropsychological performance. A significant interaction was found between LD and history of multiple concussions and LD on 2 neuropsychological measures (Trail-Making Test, Form B [P=.007] and Symbol Digit Modalities Test [P=.009]), indicating poorer performance for the group with LD and multiple concussions compared with other groups. A discriminant function analysis using neuropsychological testing of athletes 24 hours after acute in-season concussion compared with controls resulted in an overall 89.5% correct classification rate. CONCLUSIONS: Our study suggests that neuropsychological assessment is a useful indicator of cognitive functioning in athletes and that both history of multiple concussions and LD are associated with reduced cognitive performance. These variables may be detrimentally synergistic and should receive further study.

Adolescent↗