Hydrogen-like Carbon Research Articles

Photoionization process of the hydrogenlike carbon ion embedded in warm and hot dense plasmas.

Complicated many-body interactions between ions and surrounding particles exist in warm and hot dense plasmas. It will significantly alter the atomic structures and dynamic properties of the embedded ions. Recently, the atomic-state-dependent (ASD) screening model has been proposed and shown to be valid for investigating the screening effect in warm and hot dense plasmas over a wide range of electron densities and temperatures. By employing the ASD model, we investigate the photoionization process for the hydrogenlike carbon ion embedded in warm and hot dense plasmas with corresponding Coulomb coupling parameter ranges of 0.05 ≤ Γ ≤ 1.16, where Γ characterizes the ratio of the average potential to thermal energy. It is found that there are stronger plasma screening effects on the ionization energy and photoionization cross section due to the negative-energy electron distributions considered in the ASD model compared to those considering only free electrons. The present results from the ASD model show reasonable agreement with the classical Debye-Hückel (DH) model in weakly coupled plasmas. However, significant deviations of the ionization energy and cross section between these two models are observed in moderately and strongly coupled plasmas, due to the approximate treatment of the plasma-electron density distribution of the DH model. In the region of low photoelectron energies, the positions of the shape resonance peaks of the cross sections obtained from the ASD model differ significantly from those of the DH model due to the different screening effects.

Self-Consistent Calculation of the Ground State of a Hydrogen-Like Carbon Atom in a Graphene Lattice

Self-Consistent Calculation of the Ground State of a Hydrogen-Like Carbon Atom in a Graphene Lattice

KLL dielectronic recombination of hydrogenlike carbon ion in Debye plasmas

The KLL dielectronic recombination (DR) process of C5+ ion embedded in Debye plasmas is investigated using the multiconfiguration Dirac-Fock method with the Debye-Hückel model potential. The resonance energies, radiative and Auger rates as well as DR cross sections are obtained for a large range of Debye screening parameters to explore the influences of the plasma screening on the KLL DR process of C5+ ion. It is found that the total radiative rates and Auger rates of the intermediate states both decrease monotonically with increasing the plasma screening, except the Auger rate for the transition 2p2 1S → 1s that changes nonmonotonically due to such screening imposed on the interaction between the configurations 1s and 2s in C5+ ion. Moreover, for the KLL DR process, blueshift and redshift phenomena are observed for the resonance energies, which originates from the dynamic variations of the energy levels of C4+ and C5+ ions in the Debye plasma. The magnitudes of the DR cross section decrease slightly when the Debye-screening effects are not so strong.

The g factor of an electron in hydrogenlike carbon and the precision determination of the electron mass

The role of the bound electron Green function in the recent high precision determination of the electron mass is discussed. Emphasis is placed on the connection to Schwinger’s use of such Green functions in his early work establishing the modern form of QED, his calculation of leading binding corrections, and his work on synchrotron radiation.

Charge-Exchange Emission from Hydrogen-Like Carbon Ions Colliding with Water Molecules

Absolute Extreme Ultraviolet emission cross-sections have been measured for collisions between C 5 + and H 2 O in the range of 0.113 to 3.75 keV/amu (170–979 km/s). These results are used to derive velocity-dependent triplet-to-singlet ratios and emission cross-sections of the Cv K-series following single-electron capture. Comparison with existing measurements of integral charge-changing cross-sections indicates that auto-ionizing multi-electron capture is a significant reactions channel. This reaction may indirectly populate the n = 2 states and thus add strength to the K α emission of Cv ions thereby co-determining the hardness ratio of K-series emission of Cv.

A Variational Solution of the Schrödinger Equation in an Inhomogeneous Central Field

The present work is devoted to the computer modeling of emission processes from the graphene surface which is a promising material for modern applications. We examine the effect of the ion field inhomogeneity on the variational solution of the Schrödinger equation for the ground state of a loosely bound electron of a hydrogen-like carbon atom, which simulates the graphene model. This shows a significant impact of the allowance for the field inhomogeneity to the ground state of the electron.

CXRS measurements of ion temperature in NBI discharges on Globus-M spherical tokamak

The thesis describes the Charge-eXchange Recombination Spectroscopy (CXRS) diagnostics setup and its application to the ion temperature determination in the NBI-heated discharges in the Globus-M spherical tokamak. Measurements of the spectral line shape of the radiation emitted by the hydrogen-like carbon ion CVI (5290.5 Å) are presented. Comparison of CXRS and Neutral Particle Analyser (NPA) data demonstrates good agreement.

The electron mass from g-factor measurements on hydrogen-like carbon 12C5+

The electron mass in atomic mass units has been determined with a relative uncertainty of (Sturm et al 2014 Nature 506 467–70), which represents a 13-fold improvement of the 2010 CODATA value (Mohr et al 2012 Rev. Mod. Phys. 84 1527–605). The underlying measurement principle combines a high-precision measurement of the Larmor-to-cyclotron frequency ratio on a single hydrogen-like carbon ion in a Penning trap with a corresponding very accurate g-factor calculation. Here, we present the measurement results in detail, including a comprehensive discussion of the systematic shifts and their uncertainties. A special focus is set on the various sources of phase jitters, which are essential for the understanding of the applied line-shape model for the g-factor resonance.

Precise energy eigenvalues of hydrogen-like ion moving in quantum plasmas

The analytic form of the electrostatic potential felt by a slowly moving test charge in quantum plasma is developed. It has been shown that the electrostatic potential is composed of two parts: the Debye-Huckel screening term and the near-field wake potential. The latter depends on the velocity of the test charge as well as on the number density of the plasma electrons. Rayleigh-Ritz variational calculation has been done to estimate precise energy eigenvalues of hydrogen-like carbon ion under such plasma environment. A detailed analysis shows that the energy levels gradually move to the continuum with increasing plasma electron density while the level crossing phenomenon has been observed with the variation of ion velocity.

Estimate of the Deposition Profile of Carbon Pellets Using a High-Speed VUV Imaging System in the LHD

The deposition profile of the impurity pellet is measured by a two-dimensional fast-framing vacuum ultraviolet (VUV) camera system in the large helical device (LHD). The fast framing camera selectively measures the emission from the hydrogen-like ions of carbon (C VI) with a frame rate of several kHz. From the emission profile of the hydrogen-like carbon ions, which are in the process of ionization, the initial deposition profile of the carbon is estimated using a simple one-dimensional transport model.

Relative energy level shifts of hydrogen-like carbon bound-states in dense matter

AbstractThe aim of the present work is the further development of the thermodynamics of hydrogen-like plasmas with densities on the order of 1027–1029 m−3 at temperatures of 106−108 K. Therefore, the Jacobi-Padé approximation for the so-called relative energy level shifts is applied to a quasineutral plasma consisting of six-fold and five-fold ionized carbon atoms and electrons. The relative energy level shift of the five-fold ionized carbon is determined by the difference between Coulomb and Debye potential, and by the kinetic energy of the particles. The shift caused by the kinetic energy (KES) has to be found considering the momentum space of the particles, so that nine-fold integrals in phase space have to be calculated. Quantum-physically, former numerical calculations of KES were only performed for particle states with zero angular quantum numbers. In the present work, a detailed, to a large extent analytical analysis of the KES is given for any angular quantum number, enabling also an improved analysis of future further-developed Jacobi-Padé formulae. Relative energy shifts of the bound-states of the fivefold ionized carbon are numerically obtained as function of the Mott parameter of the plasma. Dependencies of the shifts on main quantum numbers and orbital quantum numbers are discussed.

Proposal for the determination of nuclear masses by high-precision spectroscopy of Rydberg states

The theoretical treatment of Rydberg states in one-electron ions is facilitated by the virtual absence of the nuclear-size correction, and fundamental constants like the Rydberg constant may be in the reach of planned high-precision spectroscopic experiments. The dominant nuclear effect that shifts transition energies among Rydberg states therefore is due to the nuclear mass. As a consequence, spectroscopic measurements of Rydberg transitions can be used in order to precisely deduce nuclear masses. A possible application of this approach to hydrogen and deuterium, and hydrogen-like lithium and carbon is explored in detail. In order to complete the analysis, numerical and analytic calculations of the quantum electrodynamic self-energy remainder function for states with principal quantum number n = 5, …, 8 and with angular momentum ℓ = n − 1 and ℓ = n − 2 are described .

Creation of highly-charged calcium ions for the g-factor determination of the bound electron

High-precision measurements of the magnetic moment of the electron bound in hydrogen-and lithium-like ions can be used to test bound-state quantum electrodynamical calculations. In the past measurements with relative experimental uncertainties as low as 2×10-9 were performed on hydrogen-like carbon and oxygen ions. In the current experiment we plan to measure the g-factor of hydrogen-like and lithium-like calcium ions. A relative uncertainty δg/g in the order of 10-9 is aspired. Here, we will give the motivation for the experiment, present the experimental techniques and first results.

Effect of strongly coupled plasma on the spectra of hydrogenlike carbon, aluminium and argon

A detailed study has been performed for estimating the orbital energies, positions and shifts of the Lyman lines of C5+, Al12+ and Ar17+ under strongly coupled plasma with a view to understand such line positions and shifts obtained in laser produced plasma experiments. The effect of strongly coupled plasma has been treated within the Ion Sphere (IS) model. Both non-relativistic and relativistic methods have been used for estimating the spectral properties. Theoretical estimates with IS model of the plasma are in conformity with the results of laser plasma experiments on these highly stripped ions. The experimental data for the systems have also been compared with the theoretical estimates using Debye screening model of the plasma with spatial confinements which gives additional restrictions to the wave functions at finite boundaries.

Towards a g-factor determination of the electron bound in highly-charged calcium ions

BOUND-state quantum electrodynamical calculations can be tested by high precision measurements of the magnetic moment of the electron bound in hydrogen-like and lithium-like ions. Measurements of hydrogen-like carbon and oxygen achieved relative experimental uncertainties as low as 2 × 10−9. In the current experiment we plan to measure the g-factor of hydrogen-like and lithium-like calcium ions. The aim is to reach a relative uncertainty ∂g/gin the order of 10−9. Here, we will give the motivation for the experiment, present the experimental techniques and the status of the experiment.

Complete two-loop correction to the bound-electrongfactor

Within a systematic approach based on dimensionally regularized nonrelativistic quantum electrodynamics, we derive a complete result for the two-loop correction to order ({alpha}/{pi}){sup 2}(Z{alpha}){sup 4} for the g factor of an electron bound in an nS state of a hydrogenlike ion. The results obtained significantly improve the accuracy of the theoretical predictions for the hydrogenlike carbon and oxygen ions and influence the value of the electron mass inferred from g-factor measurements.

Temperature measurement of a single ion in a Penning trap

The present work is concerned with the association of a temperature to a single ion stored in a Penning ion trap. Several methods are described which allow to determine the temperature by measurements of the ion’s cyclotron and axial trapping frequencies. Recent results of a measurement on a hydrogen-like carbon ion 12C5 + by use of mode coupling are presented and possible further applications are discussed.

Effect of frequency redistribution in X-ray laser modeling

Calculations are presented of the spectral emissivity corrected for higher-order processes such as photon scattering. Usually, photon scattering is taken into account by postulating a complete frequency redistribution approximation, i.e., same absorption and emission spectra. However, cases exist in hot and dense plasmas for which partial frequency redistribution and angular redistribution play an important role for the radiative transfer mechanisms. Examples of X-ray lasers based on neon-like germanium ion emitters and hydrogen-like carbon ion emitters are considered.

New value for the electron’s mass—theoretical foundations

We elucidate all theoretical contributions that enter theg factor in hydrogen-likeatoms. The gfactor of hydrogen-like carbon plays a crucial role in the determination of the electron’s mass.For higher Z,we explicitly demonstrate that neither the imprecisely known nuclear size and shape,nor the nuclear polarization, set a limit to investigations on quantum electrodynamicsby g-factorexperiments, if measurements are performed on more than one state of the samesystem.

Double Penning trap technique for precise g factor determinations in highly charged ions

We present a detailed description of an experiment to determine the magnetic moment of an electron bound in hydrogen-like carbon. This forms a high-accuracy test of bound-state quantum electrodynamics. Special emphasis is given to the discussion of systematic uncertainties which limit our present accuracy. The described experimental setup may also be used for the determination of g factors in other highly charged ions.