582 research outputs found
Relativistic transition wavelenghts and probabilities for spectral lines of Ne II
Transition wavelengths and probabilities for several 2p4 3p - 2p4 3s and 2p4
3d - 2p4 3p lines in fuorine-like neon ion (NeII) have been calculated within
the multiconfiguration Dirac-Fock (MCDF) method with quantum electrodynamics
(QED) corrections. The results are compared with all existing experimental and
theoretical data
Coordinate-space approach to the bound-electron self-energy: Self-Energy screening calculation
The self-energy screening correction is evaluated in a model in which the
effect of the screening electron is represented as a first-order perturbation
of the self energy by an effective potential. The effective potential is the
Coulomb potential of the spherically averaged charge density of the screening
electron. We evaluate the energy shift due to a , ,
, or electron screening a , ,
, or electron, for nuclear charge Z in the range . A detailed comparison with other calculations is made.Comment: 54 pages, 10 figures, 4 table
QED self-energy contribution to highly-excited atomic states
We present numerical values for the self-energy shifts predicted by QED
(Quantum Electrodynamics) for hydrogenlike ions (nuclear charge ) with an electron in an , 4 or 5 level with high angular momentum
(). Applications include predictions of precision transition
energies and studies of the outer-shell structure of atoms and ions.Comment: 20 pages, 5 figure
Recent Approaches for Chemical Speciation and Analysis by Electrospray Ionization (ESI) Mass Spectrometry
In recent years, the chemical speciation of several species has been increasingly monitored and investigated, employing electrospray ionization mass spectrometry (ESI-MS). This soft ionization technique gently desolvates weak metal\u2013ligand complexes, taking them in the high vacuum sectors of mass spectrometric instrumentation. It is, thus, possible to collect information on their structure, energetics, and fragmentation pathways. For this reason, this technique is frequently chosen in a synergistic approach to investigate competitive ligand exchange-adsorption otherwise analyzed by cathodic stripping voltammetry (CLE-ACSV). ESI-MS analyses require a careful experimental design as measurement may face instrumental artifacts such as ESI adduct formation, fragmentation, and sometimes reduction reactions. Furthermore, ESI source differences of ionization efficiencies among the detected species can be misleading. In this mini-review are collected and critically reported the most recent approaches adopted to mitigate or eliminate these limitations and to show the potential of this analytical technique
Perturbation Approach to the Self Energy of non-S Hydrogenic States
We present results on the self-energy correction to the energy levels of
hydrogen and hydrogenlike ions. The self energy represents the largest QED
correction to the relativistic (Dirac-Coulomb) energy of a bound electron. We
focus on the perturbation expansion of the self energy of non-S states, and
provide estimates of the so-called A60 perturbative coefficient, which can be
considered as a relativistic Bethe logarithm. Precise values of A60 are given
for many P, D, F and G states, while estimates are given for other electronic
states. These results can be used in high-precision spectroscopy experiments in
hydrogen and hydrogenlike ions. They yield the best available estimate of the
self-energy correction of many atomic states.Comment: 18 pages (in 2-column format), 21 figures. Version 2 (June 20, 2003)
includes minor modification
Toward high-precision values of the self energy of non-S states in hydrogen and hydrogen-like ions
The method and status of a study to provide numerical, high-precision values
of the self-energy level shift in hydrogen and hydrogen-like ions is described.
Graphs of the self energy in hydrogen-like ions with nuclear charge number
between 20 and 110 are given for a large number of states. The self-energy is
the largest contribution of Quantum Electrodynamics (QED) to the energy levels
of these atomic systems. These results greatly expand the number of levels for
which the self energy is known with a controlled and high precision.
Applications include the adjustment of the Rydberg constant and atomic
calculations that take into account QED effects.Comment: Minor changes since previous versio
Analytical Method for Quantification of Several Phthalate Acid Esters by Gas Chromatography-Mass Spectrometry in Coffee Brew Samples
Several phthalate acid esters (PAEs), often called phthalate esters or phthalates, are substances classified as harmful due to their carcinogenic and mutagenic properties, and moreover, as dangerous for humans because they interfere with the endocrine system. In general, phthalic esters are used as plasticizers for different polymers and more other consumer products. In the present study, we describe a simple method to quantify PAEs in coffee brew using a liquid-liquid extraction without purification processes through analysing the obtained organic phase by GCMS in the single ion monitoring mode. The totals of single PAEs, in coffee brew samples analysed by us, are in the range of 159-5305 mu g L-1. Considering that, on average, a person drinks three cups (total 90 mL) of the aforementioned drink per day, this will lead to the uptake of a total 14 to 477 mu g of phthalates
A Short Review of Simple Analytical Methods for the Evaluation of PAHs and PAEs as Indoor Pollutants in House Dust Samples
Studies on indoor air quality are indispensable when considering that people spend approximately 85% of their time in confined environments. This short review mostly takes into consideration research that uses passive samplers to evaluate the quality of indoor environments (houses, school, cars, etc.). This short review summarizes most analytical methods to detect and quantify PAHs and PAEs in house dust used as a passive sampler. The objective of house dust analysis is to identify the presence, amount and distribution of specific hazardous substances in confined spaces and, if possible, to identify their sources. Household dust and the compounds present in it can enter the human body by inhalation, non-food ingestion and absorption through the skin. The observed differences in concentrations of house dust may also indicate important differences in the chemical and physical nature of pollutants caused by air filtration and absorption during the migration of ambient air into the indoor environment
Effects of Fe doping in La1/2Ca1/2MnO3
The effect of Fe doping in the Mn site on the magnetic, transport and
structural properties of polycrystalline La1/2Ca1/2MnO3 was studied. Doping
with low Fe concentration (< 10%) strongly affects electrical transport and
magnetization. Long range charge order is disrupted even for the lowest doping
level studied (~2%). For Fe concentration up to 5% a ferromagnetic state
develops at low temperature with metallic like conduction and thermal
hysteresis. In this range, the Curie temperature decreases monotonously as a
function of Fe doping. Insulating behavior and a sudden depression of the
ferromagnetic state is observed by further Fe doping.Comment: 2 pages, presented at ICM2000, to appear in JMM
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