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Paul Indelicato

Publications and source records attributed to Paul Indelicato.

At least 55 records · Page 3Linked to original sources
arXiv2012

Mass- and field-shift isotope parameters for the $2s - 2p$ resonance doublet of lithium-like ions

It was recently shown that dielectronic recombination measurements can be used for accurately inferring changes in the nuclear mean-square charge radii of highly-charged lithium-like neodymium [Brandau et al., Phys. Rev. Lett. 100 073201 (2008)]. To make use of this method to derive information about the nuclear charge distribution for other elements and isotopes, accurate electronic isotope shift parameters are required. In this work, we calculate and discuss the relativistic mass- and field-shift factors for the two $2s ^{2}S_{1/2} - 2p ^{2}P^{o}_{1/2,3/2}$ transitions along the lithium isoelectronic sequence. Based on the multiconfiguration Dirac-Hartree-Fock method, the electron correlation and the Breit interaction are taken into account systematically. The analysis of the isotope shifts for these two transitions along the isoelectronic sequence demonstrates the importance and competition between the mass shifts and the field shifts.

physics.atom-ph↗
arXiv2011

Differential energy measurement between He- and Li-like uranium intra-shell transitions

We present the first clear identification and highly accurate measurement of the intra-shell transition $1s2p\, ^3P_2 \to 1s2s\, ^3S_1$ of He-like uranium performed via X-ray spectroscopy. The present experiment has been conducted at the gas-jet target of the ESR storage ring in GSI (Darmstadt, Germany) where a Bragg spectrometer, with a bent germanium crystal, and a Ge(i) detector were mounted. Using the ESR deceleration capabilities, we performed a differential measurement between the $1s2p\, ^3P_2 \to 1s2s\, ^3S_1$ He-like U transition energy, at 4510 eV, and the $1s^22p\ ^2P_{3/2} \to 1s^22s\, ^2S_{1/2}$ Li-like U transition energy, at 4460 eV. By a proper choice of the ion velocities, the X-ray energies from the He- and Li-like ions could be measured, in the laboratory frame, at the same photon energy. This allowed for a drastic reduction of the experimental systematic uncertainties, principally due to the Doppler effect, and for a comparison with the theory without the uncertainties arising from one-photon QED predictions and nuclear size corrections.

physics.atom-ph↗
arXiv2010

Analytical study of electrostatic ion beam traps

The use of electrostatic ion beam traps require to set many potentials on the electrodes (ten in our case), making the tuning much more difficult than with quadrupole traps. In order to obtain the best trapping conditions, an analytical formula giving the electrostatic potential inside the trap is required. In this paper, we present a general method to calculate the analytical expression of the electrostatic potential in any axisymmetric set of electrodes. We use conformal mapping to simplify the geometry of the boundary. The calculation is then performed in a space of simple geometry. We show that this method, providing excellent accuracy, allows to obtain the potential on the axis as an analytic function of the potentials applied to the electrodes, thus leading to fast, accurate and efficient calculations. We conclude by presenting stability maps depending on the potentials that enabled us to find the good trapping conditions for oxygen 4+ at much higher energies than what has been achieved until now.

physics.atom-ph↗
arXiv2010

Electronic temperatures, densities and plasma X-ray emission of a 14.5 GHz Electron-Cyclotron Resonance Ion Source

We have performed a systematic study of the Bremsstrahlung emission from the electrons in the plasma of a commercial 14.5 GHz Electron-Cyclotron Resonance Ion Source. The electronic spectral temperature and the product of ionic and electronic densities of the plasma are measured by analyzing the Bremsstrahlung spectra recorded for several rare gases (Ar, Kr, Xe) as a function of the injected power. Within our uncertainty, we find an average temperature of ? 48 keV above 100W, with a weak dependency on the injected power and gas composition. Charge state distributions of extracted ion beams have been determined as well, providing a way to disentangle the ionic density from the electronic density. Moreover X-ray emission from highly charged argon ions in the plasma has been observed with a high-resolution mosaic crystal spectrometer, demonstrating the feasibility for high-precision measurements of transition energies of highly charged ions, in particular of the magnetic dipole (M1) transition of He-like of argon ions.

physics.plasm-ph↗
arXiv2009

Doppler-tuned Bragg Spectroscopy of Excited Levels in He-Like Uranium: a discussion of the uncertainty contributions

We present the uncertainty discussion of a recent experiment performed at the GSI storage ring ESR for the accurate energy measurement of the He-like uranium 1s2p3P2- 1s2s3S1 intra-shell transition. For this propose we used a Johann-type Bragg spectrometer that enables to obtain a relative energy measurement between the He-like uranium transition, about 4.51 keV, and a calibration x-ray source. As reference, we used the Ka fluorescence lines of zinc and the Li-like uranium 1s22p2P3/2 - 1 s22s 2S1/2 intra-shell transition from fast ions stored in the ESR. A comparison of the two different references, i.e., stationary and moving x-ray source, and a discussion of the experimental uncertainties is presented.

physics.atom-ph↗
arXiv2009

Production and decay of Sulphur excited species in a ECRIS plasma

The most important processes for the creation of S12+ to S14+ ions excited states from the ground configurations of S9+ to S14+ ions in an electron cyclotron resonance ion source, leading to the emission of K X-ray lines, are studied. Theoretical values for inner-shell excitation and ionization cross sections, including double KL and triple KLL ionization, transition probabilities and energies for the deexcitation processes, are calculated in the framework of the multi-configuration Dirac-Fock method. With reasonable assumptions about the electron energy distribution, a theoretical K$α$ X-ray spectrum is obtained, which is compared to recent experimental data.

physics.atom-ph↗
arXiv2009

Negative continuum effects on the two-photon decay rates of hydrogen-like ions

Two--photon decay of hydrogen--like ions is studied within the framework of second--order perturbation theory, based on relativistic Dirac's equation. Special attention is paid to the effects arising from the summation over the negative--energy (intermediate virtual) states that occurs in such a framework. In order to investigate the role of these states, detailed calculations have been carried out for the $2s_{1/2} - 1s_{1/2}$ and $2p_{1/2} - 1s_{1/2}$ transitions in neutral hydrogen H as well as for hydrogen--like xenon Xe$^{53+}$ and uranium U$^{91+}$ ions. We found that for a correct evaluation of the total and energy--differential decay rates, summation over the negative--energy part of Dirac's spectrum should be properly taken into account both for high--$Z$ and low--$Z$ atomic systems.

physics.atom-ph↗
arXiv2009

Observation of the 2p3/2 -> 2s1/2 intra-shell transition in He-like uranium

We present the first observation of the 1s2p 3P2 ? 1s2s 3S1 transition in He-like uranium. The experiment was performed at the internal gas-jet target of the ESR storage ring at GSI exploiting a Bragg crystal spectrometer and a germanium solid state detector. Using the 1s2 2p 2P3/2 ? 1s2 2s 2S1/2 transition in Li-like uranium as reference and the deceleration capabilities of the ESR storage rings, we obtained the first evaluation of the He-like heavy ion intra-shell transition energy.

physics.atom-ph↗
arXiv2009

Relativistic K shell decay rates and fluorescence yields for Zn, Cd and Hg

In this work we use the multiconfiguration Dirac-Fock method to calculate the transition probabilities for all possible decay channels, radiative and radiationless, of a K shell vacancy in Zn, Cd and Hg atoms. The obtained transition probabilities are then used to calculate the corresponding fluorescence yields which are compared to existing theoretical, semi-empirical and experimental results.

physics.atom-ph↗
arXiv2009

High-accuracy Complete Active Space multiconfiguration Dirac-Hartree-Fock calculations of hyperfine structure constants of the gold atom

The multiconfiguration Dirac-Hartree-Fock (MCDHF) model has been employed to calculate the expectation values for the hyperfine splittings of the 5d96s2 2D3/2 and 5d96s2 2D5/2 levels of atomic gold. One-, two-, and three-body electron correlation effects involving all 79 electrons have been included in a systematic manner. The approximation employed in this study is equivalent to a Complete Active Space (CAS) approach. Calculated electric field gradients, together with experimental values of the electric quadrupole hyperfine structure constants, allow us to extract a nuclear electric quadrupole moment Q(197Au)=521.5(5.0) mb.

physics.atom-ph↗
arXiv2009

MCDHF calculations of the electric dipole moment of radium induced by the nuclear Schiff moment

The multiconfiguration Dirac-Hartree-Fock theory (MCDHF) has been employed to calculate the electric dipole moment of the 7s6d 3D2 state of radium induced by the nuclear Schiff moment. The results are dominated by valence and core-valence electron correlation effects. We show that the correlation effects can be evaluated in a converged series of multiconfiguration expansions.

physics.atom-ph↗
arXiv2009

Resonant effects on the two-photon emission from hydrogenic ions

A theoretical study the all two-photon transitions from initial bound states with ni = 2, 3 in hydrogenic ions is presented. High-precision values of relativistic decay rates for ions with nuclear charge in the range 1 =< Z =< 92 are obtained through the use of finite basis sets for the Dirac equation constructed from B-splines. We also report the spectral (energy) distributions of several resonant transitions, which exhibit interesting structures, such as zeroes in the emission spectrum, indicating that two-photon emission is strongly suppressed at certain frequencies. We compare two different approaches (the Line Profile Approach (LPA) and the QED approach based on the analysis of the relativistic two-loop self energy (TLA)) to regularize the resonant contribution to the decay rate. Predictions for the pure two-photon contributions obtained in these approaches are found to be in a good numerical agreement.

physics.atom-ph↗
arXiv2009

Analysis of X-ray spectra emitted from laser-produced plasmas of uranium

In this paper, we used the multiconfiguration Dirac-Fock method to generate theoretical X-ray spectra for Co-, Ni-, Cu-, Zn-, Ga-, Ge-, As-, Se-, Br-, Kr-, and Rb-like uranium ions. Using the distribution of these ions in a laser-produced plasma, for different plasma temperatures, we generate theoretical spectra, which are compared to experimental data.

physics.atom-ph↗
arXiv2007

QED and relativistic corrections in superheavy elements

In this paper we review the different relativistic and QED contributions to energies, ionic radii, transition probabilities and Landé $g$-factors in super-heavy elements, with the help of the MultiConfiguration Dirac-Fock method (MCDF). The effects of taking into account the Breit interaction to all orders by including it in the self-consistent field process are demonstrated. State of the art radiative corrections are included in the calculation and discussed. We also study the non-relativistic limit of MCDF calculation and find that the non-relativistic offset can be unexpectedly large.

physics.atom-ph↗
arXiv2007

Hyperfine Quenching of the $4s4p ^{3}P_{0}$ Level in Zn-like Ions

In this paper, we used the multiconfiguration Dirac-Fock method to compute with high precision the influence of the hyperfine interaction on the $[Ar]3d^{10} 4s4p ^3P_0$ level lifetime in Zn-like ions for stable and some quasi-stable isotopes of nonzero nuclear spin between Z=30 and Z=92. The influence of this interaction on the $[Ar]3d^{10} 4s4p ^3P_1 - [Ar]3d^{10} 4s4p ^3P_0$ separation energy is also calculated for the same ions.

physics.atom-ph↗
arXiv2007

A Quantum Similarity Study of Atomic Density Functions: Insights from Information Theory and the Role of Relativistic Effects

A novel quantum similarity measure (QSM) is constructed based on concepts from information theory. In an application of QSM to atoms, the new QSM and its corresponding quantum similarity index (QSI) are evaluated throughout the periodic table, using the atomic electron densities and shape functions calculated in the Hartree-Fock approximation. The periodicity of Mendeleev's table is regained for the first time through the evaluation of a QSM. Evaluation of the information theory based QSI demonstrates, however, that the patterns of periodicity are lost due to the renormalization of the QSM, yielding chemically less appealing results for the QSI. A comparison of the information content of a given atom on top of a group with the information content of the elements in the subsequent rows reveals another periodicity pattern. Relativistic effects on the electronic density functions of atoms are investigated. Their importance is quantified in a QSI study by comparing for each atom, the density functions evaluated in the Hartree-Fock and Dirac-Fock approximations. The smooth decreasing of the relevant QSI along the periodic table illustrates in a quantitative way the increase of relativistic corrections with the nuclear charge.

physics.atom-ph↗
arXiv2007

Relativistic calculations of pionic and kaonic atoms hyperfine structure

We present the relativistic calculation of the hyperfine structure in pionic and kaonic atoms. A perturbation method has been applied to the Klein-Gordon equation to take into account the relativistic corrections. The perturbation operator has been obtained \textit{via} a multipole expansion of the nuclear electromagnetic potential. The hyperfine structure of pionic and kaonic atoms provide an additional term in the quantum electrodynamics calculation of the energy transition of these systems. Such a correction is required for a recent measurement of the pion mass.

physics.atom-ph↗