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A broadband photon echo effect in a three level A-type system interacting with two laser fields is investigated theoretically. Inspired by the emerging field of nuclear quantum optics which typically deals with very narrow resonances, we consider broadband probe pulses that couple to the system in the presence of an inhomogeneous control field. We show that such a setup provides an all-electromagnetic-field solution to implement high bandwidth photon echoes, which are easy to control, store and shape on a short time scale and, therefore, may speed up future photonic information processing. The time compression of the echo signal and possible applications for quantum memories are discussed. [ABSTRACT FROM AUTHOR]

Abstract: Electroweak processes in high-energy lepton collisions are considered in a situation where the incident center-of-mass energy lies below the reaction threshold, but is boosted to the required level by subsequent laser acceleration. Within the framework of laser-dressed quantum field theory, we study the laser-boosted process in detail and specify the technical demands needed for its experimental realization. Further, we outline possible qualitative differences to field-free processes regarding the detection of the produced Higgs bosons. [Copyright &y& Elsevier]

The dynamics of an electron in a strong laser field can be significantly altered by radiation reaction. This usually results in a strongly damped motion, with the electron losing a large fraction of its initial energy. Here we show that the electron dynamics in a bichromatic laser pulse can be indirectly controlled by a comparatively small radiation reaction force through its interplay with the Lorentz force. By changing the relative phase between the two frequency components of the bichromatic laser field, an ultrarelativistic electron bunch colliding head-on with the laser pulse can be deflected in a controlled way, with the deflection angle being independent of the initial electron energy. The effect is predicted to be observable with laser powers and intensities close to those of current state-of-the-art petawatt laser systems. [ABSTRACT FROM AUTHOR]

Coherent control of nuclear pumping in a three-level system driven by x-ray light is investigated. In single nuclei the pumping performance is determined by the branching ratio of the excited state populated by the x-ray pulse. Our results are based on the observation that in ensembles of nuclei, cooperative excitation and decay leads to a greatly modified nuclear dynamics which we characterize by a time-dependent cooperative branching ratio. We discuss prospects of steering the x-ray pumping by coherently controlling the cooperative decay. First, we study an ideal case with purely superradiant decay and perfect control of the cooperative emission. A numerical analysis of x-ray pumping in nuclear forward scattering with coherent control of the cooperative decay via externally applied magnetic fields is presented. Next, we provide an extended survey of nuclei suitable for our scheme, and propose proof-of-principle implementations already possible with typical Mössbauer nuclei such as 57Fe. Finally, we discuss the application of such control techniques to the population or depletion of long-lived nuclear states. [ABSTRACT FROM AUTHOR]

A new implementation of the split-operator method for calculating the time-evolution of Dirac wave functions is presented. With the help of self-adaptive numerical grids we are able to study the dynamics of an initially free electronic Dirac wave packet under the influence of an ultra-intense laser pulse and its scattering at a highly charged ion. Furthermore, we provide the necessary tools for constructing the Dirac ground state wave function of any single-electron ion and demonstrate them for hydrogenic oxygen. Bound Dirac dynamics in a super-strong laser field is finally investigated. [Copyright &y& Elsevier]

The dressing of atomic states in a strong laser field modifies the structure of the incoherently scattered fraction of the laser intensity, which is described to a good approximation by the Mollow spectrum. The incoherent spectrum is generated by the fluctuations of the atomic dipole moment about its expectation value, and the positions of the peaks are approximately given by the energy differences between the dressed atomic energy levels. In this paper, we investigate radiative corrections received by the dressed states. Our calculations are motivated by the quest to understand in detail the interplay of a bound electron dressed by the highly populated laser mode and its interaction with the vacuum modes. Alternatively, this may be seen as an electron experiencing modified stimulated and spontaneous radiative corrections in a vacuum tailored by the laser field. We obtain dressed self-energy shifts that depend on the Rabi flopping frequency (and in turn on the laser intensity) and on the detuning of the laser field relative to the atomic resonance frequency. We find that the dressed radiative corrections differ in a nontrivial manner from the radiative shifts of the ‘bare’ atomic states. [Copyright &y& Elsevier]

Coherent light pulse propagation is investigated in a medium of three-level atoms with two possibly closely spaced upper levels without the presence of any auxiliary driving laser fields. We derive an analytic expression for the group velocity in this system and demonstrate that it may be very low along with a small pulse distortion for a certain range of intensities. The group velocity is shown to depend sensitively on the upper level splitting and may thus be conveniently controlled by a magnetic field rather than an extra laser field. [Copyright &y& Elsevier]

Laser pulses can reach such high intensities nowadays that atoms exposed to them ionize virtually instantaneously. The extracted electrons are then accelerated to velocities nonnegligible to the speed of light. What remains are multiply charged ions with their most loosely bound outer electrons equally undergoing relativistic dynamics. These may temporarily escape from the vicinity of the ionic core, extract relativistic energies from the laser field and later recollide with the ionic core. The extremely large energies exchanged may be emitted in the form of coherent high-frequency light which is beneficial when an upconversion of frequencies is requested. Signatures of the magnetic field component of the laser field, the relativistic mass shift and spin–orbit coupling characterize the quantum relativistic dynamics. The existence of more than one active electron within the ion and that of more than one atom in gases or solids complicate the theoretical understanding considerably but simple pictures are often possible to a reasonable approximation. [ABSTRACT FROM AUTHOR]

A recent nuclear physics experiment [C.J. Chiara et al., Nature (London) 554, 216 (2018)] reports the first direct observation of nuclear excitation by electron capture (NEEC) in the depletion of the 93mMo isomer. The experiment used a beam-based setup in which Mo highly charged ions with nuclei in the isomeric state 93mMo at 2.4 MeV excitation energy were slowed down in a solid-state target. In this process, nuclear excitation to a higher triggering level led to isomer depletion. The reported excitation probability Pexc=0.01 was solely attributed to the so-far unobserved process of NEEC in lack of a different known channel of comparable efficiency. In this work, we investigate theoretically the beam-based setup and calculate excitation rates via NEEC using state-of-the-art atomic structure and ion stopping-power models. For all scenarios, our results disagree with the experimental data by approximately 9 orders of magnitude. This stands in conflict with the conclusion that NEEC was the excitation mechanism behind the observed depletion rate. [ABSTRACT FROM AUTHOR]

A relativistic electron-positron beam propagating through a magnetized electron-ion plasma is shown to generate both circularly and linearly polarized synchrotron radiations, which is intrinsically linked with asymmetric energy dissipation of the pair beam during the filamentation instability dynamics in the background plasma. The ratio of both polarizations |⟨Pcirc⟩/⟨Plin⟩|∼0.15, occurring for a wide range of beam-plasma parameters, can help in understanding the recent observation of circularly polarized radiation from gamma-ray bursts. [ABSTRACT FROM AUTHOR]

A Zevatron is an accelerator scheme envisaged to accelerate particles to ZeV energies (1 ZeV = 1021 eV). Schemes, most notably the internal shock model, have been proposed to explain the acceleration of ultra-high-energy cosmic-ray particles that have been sporadically detected reaching Earth since 1962. Here, the cyclotron auto-resonance acceleration (CARA) mechanism is tailored and used to demonstrate the possible acceleration of particles ejected as a result of violent astrophysical processes such as the merger of a binary system or a supernova explosion. Such events result in emission of highly energetic particles and ultra-intense beamed radiation. In the simultaneous presence of a super-strong magnetic field, the condition for cyclotron auto-resonance may be met. Thus CARA can act like a booster for particles pre-accelerated inside their progenitor by shock waves, possibly among other means. As examples, it is shown that nuclei of hydrogen, helium, and iron-56, may reach ZeV energies by CARA, under which conditions the particles, while gyrating around the lines of an ultra-strong magnetic field, also surf on the waves of a super-intense radiation field. When radiation-reaction is taken into account, it is shown that the ZeV energy gained by a particle can fall off by less than an order of -magnitude if the resonance condition is missed by roughly less than 20%. [ABSTRACT FROM AUTHOR]

A scheme is put forward to generate fully coherent x-ray lasers based on population inversion in highly charged ions, created by fast inner-shell photoionization using broadband x-ray free-electron-laser (XFEL) pulses in a laser-produced plasma. Numerical simulations based on the Maxwell–Bloch theory show that one can obtain high-intensity, femtosecond x-ray pulses of relative bandwidths Δω/ω = 10−5–10−7, by orders of magnitude narrower than in x-ray free-electron-laser pulses for discrete wavelengths down to the sub-ångström regime. Such x-ray lasers can be applicable in the study of x-ray quantum optics and metrology, investigating nonlinear interactions between x-rays and matter, or in high-precision spectroscopy studies in laboratory astrophysics. [ABSTRACT FROM AUTHOR]

Ongoing progress in laser and accelerator technology opens new possibilities in high-field science, notably to investigate the largely unexplored strong-field quantum electrodynamics (SFQED) regime where electron-positron pairs can be created directly from light-matter or even light-vacuum interactions. Laserless strategies such as beam-beam collisions have also been proposed to access the nonperturbative limit of SFQED. Here we report on a concept to probe SFQED by harnessing the interaction between a high-charge, ultrarelativistic electron beam and a solid conducting target. When impinging onto the target surface, the beam self fields are reflected, partly or fully, depending on the beam shape; in the rest frame of the beam electrons, these fields can exceed the Schwinger field, thus triggering SFQED effects such as quantum nonlinear inverse Compton scattering and nonlinear Breit-Wheeler electron-positron pair creation. Through reduced modeling and kinetic numerical simulations, we show that this single-beam setup can achieve interaction conditions similar to those envisioned in beam-beam collisions, but in a simpler and more controllable way owing to the automatic overlap of the beam and driving fields. This scheme thus eases the way to precision studies of SFQED and is also a promising milestone towards laserless studies of nonperturbative SFQED. The largely unexplored strong-field QED regime in high-field science could be probed using high-energy particle beams and high-intensity lasers. Here the authors propose a concept to probe strong-field QED by harnessing the interaction between an ultrarelativistic electron beam and a solid and whose setup is based on the collision between the high-density beam and the self-fields reflected at the plasma boundary. [ABSTRACT FROM AUTHOR]

The article reports on the success of researchers at Lawrence Livermore National Laboratory in California to generate copious amounts of positrons using superintense short laser pulses. They found that these positrons formed the highest antimatter densities ever created in the world. Moreover, intense positron sources are also found to generate dense targets of cold positronium atoms.

Ultra strong electromagnetic fields can lead to spontaneous creation of single or multiple electron–positron pairs. A quantum field theoretical treatment of the pair creation process combined with numerical methods provides a description of the fermionic quantum field state, from which all observables of the multiple electron–positron pairs can be inferred. This allows to study the complex multi-particle dynamics of electron–positron pair creation in-depth, including multi-pair statistics as well as momentum distributions and spin. To illustrate the potential benefit of this approach, it is applied to the intermediate regime of pair creation between nonperturbative Schwinger pair creation and perturbative multiphoton pair creation where the creation of multi-pair states becomes nonnegligible but cascades do not yet set in. Furthermore, it is demonstrated how spin and helicity of the created electrons and positrons are affected by the polarization of the counterpropagating laser fields, which induce the creation of electron–positron pairs. [ABSTRACT FROM AUTHOR]

The absolute atomic mass of 208 Pb has been determined with a fractional uncertainty of 7 × 10 - 11 by measuring the cyclotron-frequency ratio R of 208 Pb 41 + to 132 Xe 26 + with the high-precision Penning-trap mass spectrometer Pentatrap and computing the binding energies E Pb and E Xe of the missing 41 and 26 atomic electrons, respectively, with the ab initio fully relativistic multi-configuration Dirac–Hartree–Fock (MCDHF) method. R has been measured with a relative precision of 9 × 10 - 12 . E Pb and E Xe have been computed with an uncertainty of 9.1 eV and 2.1 eV, respectively, yielding 207.976 650 571 (14) u ( u = 9.314 941 024 2 (28) × 10 8 eV/c 2 ) for the 208 Pb neutral atomic mass. This result agrees within 1.2 σ with that from the Atomic-Mass Evaluation (AME) 2020, while improving the precision by almost two orders of magnitude. The new mass value directly improves the mass precision of 14 nuclides in the region of Z = 81–84 and is the most precise mass value with A > 200 . Thus, the measurement establishes a new region of reference mass values which can be used e.g. for precision mass determination of transuranium nuclides, including the superheavies. [ABSTRACT FROM AUTHOR]

We present an exact plane-wave-based analysis of the vacuum acceleration, to energy gradients in the TeV/m range, of a single electron, using two laser beams crossing at an arbitrary angle. Our analysis of the dynamics evolves from analytic solutions to the relativistic equations of motion and predicts that, for a given laser intensity, a unique crossing angle maximizes the energy gain due to constructive interference. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

This document is a correction notice for an article titled "High-precision mass measurement of doubly magic 208Pb" published in the European Physical Journal A. The correction states that there was an error in the original paper regarding the sign of the image charge shift (ICS), which should have been negative. This error affected the final mass value and the masses of connected isotopes. The corrected cyclotron frequency ratio and the atomic mass value of 208Pb are provided, along with the corrected mass excess. The correction also includes a table with new mass values for affected nuclides. The document provides necessary corrections and clarifications to the previous publication, ensuring accuracy in the research findings. [Extracted from the article]

Two oppositely charged particles created within a microscopic space-time region can be separated, accelerated over a much larger distance, and brought to a recollision by a laser field. Consequently, new reactions become feasible, where the energy absorbed by the particles is efficiently released. By investigating the laser-dressed polarization operator, we identify a new contribution describing high-energy recollisions experienced by an electron-positron pair generated by pure light when a gamma photon impinges on an intense, linearly polarized laser pulse. The energy absorbed in the recollision process over the macroscopic laser wavelength corresponds to a large number of laser photons and can be exploited to prime high-energy reactions. Thus, the recollision contribution to the polarization operator differs qualitatively and quantitatively from the well-known one, describing the annihilation of an electronpositron pair within the microscopic formation region. [ABSTRACT FROM AUTHOR]

The intermediate domain of strong-field ionization between the tunneling and multiphoton regimes is investigated using the strong-field approximation and the imaginary-time method. An intuitive model for the dynamics is developed which describes the ionization process within a nonadiabatic tunneling picture with a coordinate dependent electron energy during the under-the-barrier motion. The nonadiabatic effects in the elliptically polarized laser field induce a transversal momentum shift of the tunneled electron wave packet at the tunnel exit and a delayed appearance in the continuum as well as a shift of the tunneling exit towards the ionic core. The latter significantly modifies the Coulomb focusing during the electron excursion in the laser field after exiting the ionization tunnel. We show that nonadiabatic effects are especially large when the Coulomb field of the ionic core is taken into account during the under-the-barrier motion. The simple man model modified with these nonadiabatic corrections provides an intuitive background for exact theories and has direct implications for the calibration of the attoclock technique. [ABSTRACT FROM AUTHOR]

Line intensities and oscillator strengths for the controversial 3C and 3D astrophysically relevant lines in neonlike Fe16+ ions are calculated. A large-scale configuration-interaction calculation of oscillator strengths is performed with the inclusion of higher-order electron-correlation effects, suggesting that these contributions cannot explain existing discrepancies between theory and experiment. Then, we investigate nonlinear dynamical effects, showing that, for strong x-ray sources, the modeling of the spectral lines by a peak with an area proportional to the oscillator strength is not sufficient. The dynamical effects give a possible resolution of discrepancies of theory and experiment found by recent measurements, which motivates the use of light-matter interaction models also valid for strong light fields in the analysis and interpretation of astrophysical and laboratory spectra. [ABSTRACT FROM AUTHOR]

Radiation-reaction effects in the interaction of an electron bunch with a superstrong focused ultrashort laser pulse are investigated in the quantum radiation-dominated regime. The angle-resolved Compton scattering spectra are calculated in laser pulses of variable duration using a semiclassical description for the radiation-dominated dynamics and a full quantum treatment for the emitted radiation. In dependence of the laser-pulse duration we find signatures of quantum radiation reaction in the radiation spectra, which are characteristic for the focused laser beam and visible in the qualitative behavior of both the angular spread and the spectral bandwidth of the radiation spectra. The signatures are robust with respect to the variation of the electron and laser-beam parameters in a large range. Qualitatively, they differ fully from those in the classical radiation-reaction regime and are measurable with presently available laser technology. [ABSTRACT FROM AUTHOR]

Although the spin is regarded as a fundamental property of the electron, there is no universally accepted spin operator within the framework of relativistic quantum mechanics. We investigate the properties of different proposals for a relativistic spin operator. It is shown that most candidates are lacking essential features of proper angular momentum operators, leading to spurious zitterbewegung (quivering motion) or violation of the angular momentum algebra. Only the Foldy–Wouthuysen operator and the Pryce operator qualify as proper relativistic spin operators. We demonstrate that ground states of highly charged hydrogen-like ions can be utilized to identify a legitimate relativistic spin operator experimentally. [ABSTRACT FROM AUTHOR]

The new regime of resonant nuclear photoexcitation rendered possible by x-ray free-electron laser beams interacting with solid state targets is investigated theoretically. Our results unexpectedly show that secondary processes coupling nuclei to the atomic shell in the created cold high-density plasma can dominate direct photoexcitation. As an example, we discuss the case of 93mMo isomer depletion for which nuclear excitation by electron capture as a secondary process is shown to be orders of magnitude more efficient than the direct laser-nucleus interaction. General arguments revisiting the role of the x-ray free-electron laser in nuclear experiments involving solid-state targets are further deduced. [ABSTRACT FROM AUTHOR]

Stimulated Raman scattering of an ultraintense laser pulse in plasmas is studied by perturbatively including the leading order term of the Landau-Lifshitz radiation reaction force in the equation of motion for plasma electrons. In this approximation, the radiation reaction force causes a phase shift in nonlinear current densities that drive the two Raman sidebands (anti-Stokes and Stokes waves), manifesting itself into the nonlinear mixing of two sidebands. This mixing results in a strong enhancement in the growth of the forward Raman scattering instability. [ABSTRACT FROM AUTHOR]

As a unique feature, the 229Th nucleus has an isomeric transition in the vacuum ultraviolet that can be accessed by optical lasers. The interference effects occurring in the interaction between coherent optical light and an ensemble of 229Th nuclei are investigated theoretically. We consider the scenario of nuclei doped in vacuum ultraviolet transparent crystals and take into account the effect of different doping sites and therefore different lattice fields that broaden the nuclear transition width. This effect is shown to come into interplay with interference effects due to the hyperfine splitting of the ground and isomeric nuclear states. We investigate possible experimentally available situations involving two-, three- and four-level schemes of quadrupole sublevels of the ground and isomeric nuclear states coupling to one or two coherent fields. Specific configurations which offer clear signatures of the isomer excitation advantageous for the more precise experimental determination of the transition energy are identified. Furthermore, it is shown that population trapping into the isomeric state can be achieved. This paves the way for further nuclear quantum optics applications with 229Th such as nuclear coherent control. [ABSTRACT FROM AUTHOR]

Interaction of an ultrastrong short laser pulse with nonprepolarized near-critical density plasma is investigated in an ultrarelativistic regime, with an emphasis on the radiative spin polarization of ejected electrons. Our particle-in-cell simulations show explicit correlations between the angle resolved electron polarization and the structure and properties of the transient quasistatic plasma magnetic field. While the magnitude of the spin signal is the indicator of the magnetic field strength created by the longitudinal electron current, the asymmetry of electron polarization is found to gauge the islandlike magnetic distribution which emerges due to the transverse current induced by the laser wave front. Our studies demonstrate that the spin degree of freedom of ejected electrons could potentially serve as an efficient tool to retrieve the features of strong plasma fields. [ABSTRACT FROM AUTHOR]

Abstract: Laser-induced nuclear recollisions following α decay in the presence of an intense laser field are investigated theoretically. We show that while an intense optical laser does not influence notably the tunneling rate in α decay, it can completely change the α particle spectrum. For intensities of , the field is strong enough to induce recollisions between the emitted α particle and the daughter nucleus. The energy gained by the α particle in the field can reach 20 MeV and suffice to trigger several types of nuclear reactions on a femtosecond time scale. Similar conclusions can be drawn about laser-induced recollisions after proton emission. Prospects for the experimental realization of laser-induced nuclear recollisions are discussed. [Copyright &y& Elsevier]