Nuclear Recoil Effect Research Articles

Nuclear Recoil Effect in the Lamb Shift of Light Hydrogenlike Atoms

We report high-precision calculations of the nuclear recoil effect to the Lamb shift of hydrogenlike atoms to the first order in the electron-nucleus mass ratio and to all orders in the nuclear binding strength parameter Zα. The results are in excellent agreement with the known terms of the Zα expansion and allow an accurate identification of the nonperturbative higher-order remainder. For hydrogen, the higher-order remainder was found to be much larger than anticipated. This result resolves the long-standing disagreement between the numerical all-order and analytical Zα-expansion approaches to the recoil effect and completely removes the second-largest theoretical uncertainty in the hydrogen Lamb shift of the 1S and 2S states.

Ionization energies along beryllium isoelectronic sequence

Ionization energies for the ground state of berylliumlike ions with nuclear charge numbers in the range Z=16-96 are rigorously evaluated. The calculations merge the ab initio QED treatment in the first and second orders of the perturbation theory in the fine-structure constant $\alpha$ with the third- and higher-order electron-correlation contributions evaluated within the Breit approximation. The nuclear recoil and nuclear polarization effects are taken into account. The accuracy of the ionization energies obtained has been significantly improved in comparison with previous calculations.

Nuclear recoil correction to the g factor of boron-like argon

The nuclear recoil effect to the g factor of boron-like ions is investigated. The one-photon-exchange correction to the nuclear recoil effect is calculated in the nonrelativistic approximation for the nuclear recoil operator and in the Breit approximation for the interelectronic-interaction operator. The screening potential is employed to estimate the higher-order contributions. The updated g-factor values are presented for the ground 2P1/2 and first excited 2P3/2 states of B-like argon 40Ar13+, which are presently being measured by the ARTEMIS group at GSI.

Relativistic calculations of the nuclear recoil effect in highly charged Li-like ions

Relativistic theory of the nuclear recoil effect in highly charged Li-like ions is considered within the Breit approximation. The normal mass shift (NMS) and the relativistic NMS (RNMS) are calculated by perturbation theory to zeroth and first orders in the parameter 1/Z. The calculations are performed using the dual kinetic balance method with the basis functions constructed from B-splines. The results of the calculations are compared with the theoretical values obtained by other methods.

Neutron-induced 37 Ar recoil ejection in Ca-rich minerals and implications for 40 Ar/ 39 Ar dating

Abstract The 40 Ar/ 39 Ar dating technique requires the transformation of 39 K into 39 Ar by neutron activation. Neutron activation has undesirable secondary effects such as interfering isotope production, and recoil of 39 Ar and 37 Ar atoms from their (dominant) targets of K and Ca. In most cases, the grains analysed are large enough (>50 μm) such that the amount of target atoms ejected from the grains is small and has a negligible effect on the ages obtained. However, increasing needs to date fine-grained rocks requires constraining, and in some cases correcting for, the effect of nuclear recoil. Previous quantitative studies of recoil loss focus mostly on 39 Ar. However, 37 Ar loss can affect the ages of Ca-rich minerals via interference corrections on 36 Ar (and, to a lesser extent, 39 Ar), yielding lower 40 Ar*/ 39 Ar K and, thus, an age spuriously too young. New results focused on 37 Ar recoil by measuring the apparent age of multi-grain populations of Ca-rich minerals including Fish Canyon plagioclase (FCp) and Hb3gr hornblende, with discrete sizes ranging from 210 to <5 µm. We use previous result on sanidine grains to correct for the 39 Ar recoil loss. For the finest fractions, FCp and Hb3gr apparent ages are younger than the 39 Ar recoil-corrected ages expected for these minerals, with a maximum deviation of −40% (FCp) and −21% (Hb3gr) reached for grains below 5 μm. We calculate 37 Ar-depletion values ranging from approximately 30 to 91% and from approximately 28 to 98% for plagioclase and hornblende, respectively. This results in x 0 values (mean thickness of the partial depletion layer) of 3.3±0.4 μm (2σ; FCp) and 3.6±1.4 μm (Hb3gr), significantly higher than suggested by current models. The reason for the substantial 37 Ar loss is not well understood, but might be related to the radiation damage caused to the mineral during irradiation. x 0 ( 39 Ar) and x 0 ( 37 Ar) values obtained in this study, along with crystal dimensions, can be used for correcting 40 Ar/ 39 Ar ages from 39 Ar and 37 Ar recoil loss. We also discuss the relevance of our results to vacuum-encapsulation studies and isotopic redistribution in fine-grained minerals. Supplementary material: Annex 1, 2 and 3 are available at www.geolsoc.org.uk/SUP18610 . Annex 1 and 2: Raw argon data corrected for blank, mass discrimination and radioactive decay for Fish Canyon plagioclase (Annex 1) and Hb3gr hornblende (Annex 2). Annex 3: Step-heating 40 Ar/ 39 Ar age spectra for FCp (Fig. A3.1) and Hb3gr (Fig. A3.2).

High-energy bremsstrahlung from polarized electrons colliding with spin-12nuclei

The Born theory for bremsstrahlung from high-energy electrons colliding with extended (finite-mass) nuclei is reexamined. Higher-order effects are included into the Born approximation by making use of the weak-potential Sommerfeld-Maue prescription in an additional contribution to the transition amplitude. Predictions are made for the differential cross section (with respect to the photon degrees of freedom) and for the polarization correlations between the incoming electron and the emitted photon. It is found that at collision energies exceeding 20 MeV the cross section as well as the polarization correlations are strongly influenced by nuclear recoil and nuclear structure effects, particularly at backward photon angles. Numerical results are presented for bremsstrahlung from 10--100 MeV electrons colliding with protons, ${}^{19}$F and ${}^{89}$Y nuclei.

Double-slit experiment with a polyatomic molecule: vibrationally resolved C 1s photoelectron spectra of acetylene

We report the first evidence for double-slit interferences in a polyatomic molecule, which we have observed in the experimental carbon 1s photoelectron spectra of acetylene (or ethyne). The spectra have been measured over the photon energy range of 310–930 eV and show prominent oscillations in the intensity ratios σg(υ)/σu(υ) for the vibrational quantum numbers υ = 0,1 and for the ratios σs(υ = 1)/σs(υ = 0) for the symmetry s = g,u. The experimental findings are in very good agreement with ab initio density functional theory (DFT) calculations and are compatible with the Cohen–Fano mechanism of coherent emission from two equivalent atomic centers. This interpretation is supported by the qualitative predictions of a simple model in which the effect of nuclear recoil is taken into account to the lowest order. Our results confirm the delocalized character of the core hole created in the primary photoionization event and demonstrate that intramolecular core-hole coherence can survive the decoherent influence associated with the asymmetric nuclear degrees of freedom which are characteristic of polyatomic molecules.

PHYSICS OF DARK MATTER IN THE LIGHT OF DARK ATOMS

Direct searches for dark matter lead to serious problems for simple models with stable neutral Weakly Interacting Massive Particles (WIMPs) as candidates for dark matter. A possibility is discussed that new stable quarks and charged leptons exist and are hidden from detection, being bound in neutral dark atoms of composite dark matter. Stable -2 charged particles O -- are bound with primordial helium in O-helium (OHe) atoms, being specific nuclear interacting form of composite Warmer than Cold dark matter. Slowed down in the terrestrial matter, OHe is elusive for direct methods of underground dark matter detection based on the search for effects of nuclear recoil in WIMP-nucleus collisions. The positive results of DAMA experiments can be explained as annual modulation of radiative capture of O-helium by nuclei. In the framework of this approach, test of DAMA results in detectors with other chemical content becomes a nontrivial task, while the experimental search of stable charged particles at LHC or in cosmic rays acquires a meaning of direct test for composite dark matter scenario.

Nuclear recoil effect on the magnetic-dipole decay rates of atomic levels

The effect of finite nuclear mass on the magnetic-dipole transition probabilities between fine-structure levels of the same term is investigated. Based on a rigorous QED approach a nonrelativistic formula for the recoil correction to first order in m_e/M is derived. Numerical results for transitions of experimental interest are presented.

Nuclear deformation effect on the binding energies in heavy ions

Nuclear deformation effects on the binding energies in heavy ions are investigated. Approximate formulas for the nuclear-size correction and the isotope shift for deformed nuclei are derived. Combined with direct numerical evaluations, these formulas are employed to reanalyze experimental data on the nuclear-charge-distribution parameters in $^{238}\text{U}$ and to revise the nuclear-size corrections to the binding energies in H- and Li-like $^{238}\text{U}$. As a result, the theoretical uncertainties for the ground-state Lamb shift in ${^{238}\text{U}}^{91+}$ and for the $2{p}_{1/2}\ensuremath{-}2s$ transition energy in ${^{238}\text{U}}^{89+}$ are significantly reduced. The isotope shift of the $2{p}_{j}\ensuremath{-}2s$ transition energies for ${^{142}\text{N}\text{d}}^{57+}$ and ${^{150}\text{N}\text{d}}^{57+}$ is also evaluated including nuclear size and nuclear recoil effects within a full QED treatment.

Nuclear recoil effects in antiprotonic and muonic atoms

Relativistic nuclear recoil effects are studied for antiprotonic and muonic atoms. The generalization of the Breit-Pauli Hamiltonian including vacuum polarization is presented. Previous treatments are corrected, and the result for the 2S{sub 12}-2P{sub 12} splitting in muonic hydrogen is updated.

Radioisotope Fractionation and Secular Disequilibrium in Performance Assessment for Geologic Disposal of Nuclear Waste

ABSTRACTTwo potential applications of radioisotope fractionation and decay-series secular disequilibrium in performance assessment for geologic repositories for nuclear waste are preferential radionuclide release in source term analysis and characterization of system closure as a measure of the capacity of the geologic system to isolate waste. A primary mechanism of radioisotope fractionation is selective release and mobility of alpha decay products because of nuclear recoil effects, which is evident in natural system data. Preferential release of radioisotopes from nuclear waste forms or solubility limiting solid phases could affect repository performance; however, consequences of differential radioisotope releases are neglected in performance assessments. Decay-series disequilibria are useful also to characterize open/closedsystem behavior in natural systems. Systems that are closed on time scales that are long relative to the half-lives of decay chain nuclides achieve secular equilibrium characterized by unit activity ratios among series nuclides. For geologic disposal of nuclear waste, measures focused on chemical system closure could capture the essential characteristics of the natural system with respect to radionuclide isolation and could be based quantitatively on uranium and thorium decay series secular equilibria/disequilibria.

QED theory of the nuclear recoil effect on the atomicgfactor

The quantum electrodynamic theory of the nuclear recoil effect on the atomic g factor to all orders in \alpha Z and to first order in m/M is formulated. The complete \alpha Z-dependence formula for the recoil correction to the bound-electron g factor in a hydrogenlike atom is derived. This formula is used to calculate the recoil correction to the bound-electron g factor in the order (\alpha Z)^2 m/M for an arbitrary state of a hydrogenlike atom.

Nuclear-chemical methods in a hard tooth tissue abrasion study

The advanced method consists in implantation—labelling of the thin surface layers of the solid objects, e.g. hard tooth tissue, by atoms of suitable natural or artificial radionuclides. Nuclides from the uranium series were implanted into the surface by using nuclear recoil effect at alpha decay of 226Ra to 222Rn, alpha decay of 222Rn to RaA, alpha decay of RaA to RaB (beta-emitter) and further alpha or beta emitters. With regard to chosen alpha detection and to the half—lives of the radionuclides, there was actually measured the activity of 222Rn, RaA and RaC’ in the thin surface layer. This was followed by the laboratory simulation of the abrasion in the system of “toothbrush—various suspensions of the tooth-pastes—hard tooth tissue (or material standard—ivory)” in specially designed device—the dentoabrasionmeter. The activities of the tissue surface measured before and after abrasion were used for calculations of the relative drop of the surface activity. On this basis the influence of various tooth-pastes containing various abrasive substances was determined.

Radioactive labeling in the study of abrasion of hard tooth tissue

Labeling the surface of hard tooth tissue samples by the nuclear recoil effect in radioactive decay was applied to study abrasion caused by abrasive components of tooth-pastes.222Rn and its short-lived decay products were implanted into the surface in vacuum. For this purpose irradiation was applied to sample placed very close to thin226Ra source. Measuring the activity before and after abrasion was used to evaluate abrasion in the system toothbrush — various suspensions of the tooth-pastes — hard tooth tissue (enamel or dentine) in a specially designed device, dentoabrasionmeter VUS 2.

QED theory of the nuclear recoil effect in atoms

The quantum electrodynamic theory of the nuclear recoil effect in atoms to all orders in $\ensuremath{\alpha}Z$ is formulated. The nuclear recoil corrections for atoms with one and two electrons over closed shells are considered in detail. The problem of the composite nuclear structure in the theory of the nuclear recoil effect is discussed.

QED of high- Z three-electron ions

The removal energies of the n = 2 states of the lithium isoelectronic sequence are calculated using many-body perturbation theory (MBPT). The included contributions are the Hartree-Fock energy, the second and third-order MBPT corrections, the Breit interaction and the first order Coulomb corrections to it, and finally nuclear recoil effects. Comparison with experiment shows a discrepancy that is the order of magnitude of, but systematically smaller than the unscreened Lamb shift. Feynman graphs whose evaluation should account for this effect are identified, and technical aspects involved in their calculation discussed. A brief review of the theory of parity nonconservation in cesium is also presented.

Effect of atomic electrons on resonant nuclear scattering

A systematic study is made of the theory of inner-shell ionisation which occurs during a resonant nuclear scattering process. Some previous treatments had emphasised the effect of nuclear recoil as an electronic excitation mechanism while others focused on the effect of the direct projectile-electron Coulomb interaction. In the present approach both excitation mechanisms are accounted for. One contribution to the transition amplitude is closely related to the approximation introduced earlier by Briggs and Lane (1981). The other components provide a generalisation of the Blair formula to include recoil effects non-perturbatively. This formula had been suggested as the basis for a determination of nuclear resonance widths. The observation of Briggs and Lane that recoil excitation can lead to a smearing of the resonance profile is extended to apply to the Blair formula. These results may be useful in future resonance studies to determine whether one is observing an intrinsic nuclear width or some average effect of a sequence of closely spaced projectile-atom resonances.

½+→½+beta decay with neutrino mass effects in the elementary particle treatment of weak interactions

We compute the effect of a nonvanishing neutrino mass on the electron spectrum of tritium beta decay using the elementary particle treatment of weak interactions. Coulomb corrections are taken into account in this formalism, as are the effects of weak magnetism and nuclear recoil. The effect of a mixture of excited atomic final states is also discussed. These corrections combine to make small changes in the shape of the end point, which could be important in determinations of the neutrino mass.RADIOACTIVITY Calculation of neutrino mass and Coulomb effects on the spectrum of $^{3}\mathrm{H}$ $\ensuremath{\beta}$ decay.

High-energy electrons from bound-muon decay

Expressions for the electron spectrum from bound-muon decay which exist in the literature are very complex. The aim of this paper is to gain some insight into these formulas. This becomes possible when the Dirac equation is used to derive Wronskian-type relations between electron and muon wave functions. We also show how a trivial modification of the formulas accounts for the nuclear-recoil effect to a very good approximation. We present numerical results to aid order-of-magnitude estimates of the bound-muon-decay contribution to the background in $\ensuremath{\mu}e$ conversion experiments. We find that the electron spectrum seems insensitive to deviations of the weak-interaction parameters from standard values.