α Decays in Superstrong Static Electric Fields

Superstrong static electric fields could deform Coulomb barriers between α clusters and daughter nuclei, and bring up the possibility of speeding up α decays. We adopt a simplified model for the spherical α emitter ²¹²Po and study its responses to superstrong static electric fields. We find that superstrong electric fields with field strengths|E|~ 0:1 MV/fm could turn the angular distribution of α emissions from isotropic to strongly anisotropic, and speed up α decays by more than one order of magnitude. We also study the influences of superstrong electric fields along the Poisotope chains, and discuss the implications of our studies on α decays in superstrong monochromatic laser fields. The study here might be helpful for future theoretical studies of α decay in realistic superstrong laser fields.     

Formation and dynamics of a plasma in superstrong laser fields including radiative and quantum electrodynamics effects

Studies of phenomena accompanying the interaction of superstrong electromagnetic fields with matter, in particular, the generation of an electron–positron plasma, acceleration of electrons and ions, and the generation of hard electromagnetic radiation are briefly reviewed. The possibility of using thin films to initiate quantum electrodynamics cascades in the field of converging laser pulses is analyzed. A model is developed to describe the formation of a plasma cavity behind a laser pulse in the transversely inhomogeneous plasma and the generation of betatron radiation by electrons accelerated in this cavity. Features of the generation of gamma radiation, as well as the effect of quantum electrodynamics effects on the acceleration of ions, at the interaction of intense laser pulses with solid targets are studied.     

On the maximum energy of electrons in the presence of a relativistic laser field

As was demonstrated by Milosevic et al. in Phys. Rev. Lett. 92, 013002 (2004), the magnetic component of a light field can be compensated for using counterpropagating matched laser beams. This makes it possible to analyze the rescattering of photoelectrons in the presence of superstrong laser fields. A formula for the maximum energy of a photoelectron is derived for the given configuration of the laser field.     

Experimental study of nuclear processes in the presence of superstrong fields of a picosecond laser plasma

Nuclear processes in the presence of the superstrong laser fields of a picosecond laser plasma are experimentally studied at a radiation intensity of 2 × 10¹⁸ W/cm² on a Neodim laser setup with a power of 10 TW. Experimental data regarding neutron generation on the surface of a deuterated target (CD₂)_n owing to the thermonuclear fusion ²H(d,n)³He and the neutron generation on the Be target due to the photonuclear reaction ⁹Be(γ,n)2α are presented. Neutron yields Y _n of 10⁶ and 10³ per 4π sr per laser pulse are obtained for the (CD₂)_n and Be targets, respectively. The alpha-particle yield is measured for the first time in the neutron-free thermonuclear reactions ¹¹B + H → 3⁴He in the laser plasma on the surface of the composite B + (CH₂)_n targets. The alpha-particle yield is 10³ per 4π sr per laser pulse.     

Interaction of an atom with superstrong laser fields

A theory of atomic interaction with a superstrong laser field has been developed. The specific feature of the suggested theory is that its small parameter is the interaction between the atom and the solenoidal part of the external field, whereas its interaction with the potential part is accurately taken into account. It follows from the reported investigation that, in calculating the interaction of atoms with superstrong fields, one must abandon calculations of multipole moments of transitions between unperturbed atomic levels, and calculate instead the atomic response, which comprises multipole moments of all orders and depends on the instantaneous field magnitude. The results are compared with calculations based on the perturbation theory in terms of the interaction Hamiltonian. Zh. éksp. Teor. Fiz. 116, 793–806 (September 1999)     

Physics of Solid-State Dielectrics: Superstrong Electric Fields

Electric strengthening with decreasing dielectric thickness allows superstrong electric fields, whose strength exceeds the breakdown one for thick dielectrics, to be created in thin layers of solid-state dielectrics without an electric breakdown. Such fields are called superstrong. In thin dielectric layers of micron thickness, the processes can be investigated which cannot be observed in thicker layers due to the onset of the breakdown. In the present paper, the results of experimental investigations of processes and phenomena taking place in thin monocrystal layers of alkali-halide crystals (AHC) in superstrong electric fields are generalized. Among these processes and phenomena are: electric currents and luminescence (electroluminescence) of AHC layers, impact excitation and electronic ionization of luminescence centers and ions of the host crystal lattice, emission of electrons, accelerated in the layer by the electric field, in vacuum, formation of point and linear defects in AHC under the action of strong and superstrong electric fields, etc. All these phenomena form a new scientific direction – physics of solid-state dielectrics: superstrong electric fields. The results of investigations of superstrong electric fields allow new approaches to the understanding of mechanisms of dielectric breakdown to be realized.     

Atom charge states, Z and comparing the ADK and cADK—Theories

During the process of adjusting the ADK-theory for the superstrong laser fields we took some part in few past years [1, 7, 8], mainly in analyzing the consequences of the influence of atom charge Z, being changed during the ionization of atoms, on the transition rate of ejected electrons. In this activity we introduced a slightly changed variant of ADK-theory [3], which we began to call corrected ADK-theory, cADK, for short [8]. Now, cADK-theory is not experimentally challenged yet, but it’s results are in accordance with many predictions [see, for instance 1, 7–9]. In present work, we used calculations of modified ionization potential of atom E _i , in order to improve formula for transition rate W _cADK. As we already discussed the transition rate dependence on the atom charges state Z [1], now we explained better the differences of the two variants of the theory, ADK and cADK. Of course, our predictions need experimental check.     

Hydrogen-like atom in a superstrong magnetic field: Photon emission and relativistic energy level shift

Following our previous work, additional arguments are presented that in superstrong magnetic fields B ? (Zα)² B ₀, B ₀ = m ² c ³/e? ≈ 4.41 × 10¹³ G, the Dirac equation and the Schrödinger equation for an electron in the nucleus field following from it become spatially one-dimensional with the only z coordinate along the magnetic field, “Dirac” spinors become two-component, while the 2 × 2 matrices operate in the {0; 3} subspace. Based on the obtained solution of the Dirac equation and the known solution of the “onedimensional” Schrödinger equation by ordinary QED methods extrapolated to the {0; 3} subspace, the probability of photon emission by a “one-dimensional” hydrogen-like atom is calculated, which, for example, for the Lyman-alpha line differs almost twice from the probability in the “three-dimensional” case. Similarly, despite the coincidence of nonrelativistic energy levels, the calculated relativistic corrections of the order of (Zα)⁴ substantially differ from corrections in the absence of a magnetic field. A conclusion is made that, by analyzing the hydrogen emission spectrum and emission spectra at all, we can judge in principle about the presence or absence of superstrong magnetic fields in the vicinity of magnetars (neutron stars and probably brown dwarfs). Possible prospects of applying the proposed method for calculations of multielectron atoms are pointed out and the possibility of a more reliable determination of the presence of superstrong magnetic fields in magnetars by this method is considered.     

Ionization of excited states of the hydrogen atom by a laser pulse

The energy spectra of electrons are calculated in the adiabatic approximation when the excited 2s, 2p, and 3d states of the hydrogen atom are ionized by a superstrong ultrashort laser pulse.     

A hydrogen atom in a superstrong magnetic field and the Zeldovich effect

We consider the problem of a hydrogen atom in a superstrong magnetic field, B? B _a =2.35×10⁹ G. The analytical formulas that describe the energy spectrum of this atom are derived for states with various quantum numbers n_ρ and m. A comparison with available calculations shows their high accuracy for B?B _a . We note that the derived formulas point to a manifestation of the Zeldovich effect, i.e., a rearrangement of the atomic spectrum under the influence of strong short-range Coulomb potential distortion. We discuss the relativistic corrections to level energies, which increase in importance with magnetic field and become significant for B?10¹⁴ G. We suggest the parameters in terms of which the Zeldovich effect has the simplest form. Analysis of our precision numerical calculations of the energy spectrum for a hydrogen atom in a constant magnetic field indicates that the Zeldovich effect is observed in the spectrum of atomic levels for superstrong fields, B?5×10¹¹ G. Magnetic fields of such strength exist in neutron stars and, possibly, in magnetic white dwarfs. We set lower limits for the fields B_min required for the manifestation of this effect. We discuss some of the properties of atomic states in a superstrong magnetic field, including their mean radii and quadrupole moments. We calculated the probabilities of electric dipole transitions between odd atomic levels and a deep ground level.     

The Zeldovich effect in a superstrong magnetic field

It follows from the analysis of the precision numerical calculations of the energy spectrum of a hydrogen atom in a static magnetic field that the Zeldovich effect (rearrangement of the atomic spectrum) in the spectrum of atomic levels is observed at superstrong magnetic fields B≥5×10₁₁ G. Magnetic fields of such strengths are reached in neutron stars and magnetic white dwarfs. We established a lower bound B_min for the fields required for this effect to occur.     

Effect of superstrong magnetic fields on thermonuclear reaction rates on the surface of magnetars

A simple and efficient screening model for studying the effects of superstrong magnetic fields （such as those of magnetars） on thermonuclear reaction rates on magnetar surfaces is proposed in this paper. The most interesting thermonuclear reactions, including hydrogen burning by the CNO cycle and helium burning by the triple alpha reaction, are investigated on the surface ofmagnetars. We find that the superstrong magnetic fields can increase the thermonuclear reaction rates by many orders of magnitude. The enhancement may have a dramatic effect on the thermonuclear runaways and bursts on the surfaces of magnetars.     

Bragg scattering of light in vacuum structured by strong periodic fields

Elastic scattering of laser radiation due to vacuum polarization by spatially modulated strong electromagnetic fields is considered. The Bragg interference arising at a specific impinging direction of the probe wave concentrates the scattered light in specular directions. The interference maxima are enhanced with respect to the usual vacuum polarization effect proportional to the square of the number of modulation periods within the interaction region. The Bragg scattering can be employed to detect the vacuum polarization effect in a setup of multiple crossed superstrong laser beams with parameters envisaged in the future Extreme Light Infrastructure.     

Relativistic theory of atom-laser interactions at very high laser intensities

The high-frequency approximation of Kristi? and Mittleman is considered in detail as a basis for the relativistic theory of atom-laser interactions. The properties of the 3D potentials are discussed. Within a one-dimensional model similar to that employed by Kylstra, Ermolaev, and Joachain in ab initio calculations on the time-dependent Dirac equation, the electron mass-shift due to dressing by a superstrong laser field is investigated. In the full domain of the laser parameters, the frequency ω and the peak field strength ?₀, the 1D bound states exhibit remarkable features. The numerical calculations show the existence of a very wide intermediate range of the field strengths where, in the zeroth order of the high-frequency approximation, the binding is stabilized by the field.     

Proton and light-ion acceleration to relativistic GeV energies by the superstrong laser radiation interacting with a structured plasma target

A new scheme is proposed for proton and light-ion acceleration to relativistic energies by superstrong laser radiation interacting with a structured plasma target. The proposal consists in the use of two-component targets consisting of heavy and light ions, where an ambipolar field is formed under the action of the ponderomotive force of incident radiation, and, in contrast to the traditional schemes, acceleration starts from the front boundary of the layer. It is shown that, for the optimized target parameters, monoenergetic GeV ion beams can be produced for radiation pulse intensities on the order of 10²¹−10²² W/cm².     

Nuclear energy generation rates on magnetar surfaces

Based on the new screening model, this paper discusses the influence of superstrong magnetic fields on nuclear energy generation rates on the surface of magnetars. The obtained result shows that the superstrong magnetic fields can increase the nuclear energy generation rates by many orders of magnitude. The enhancement may have a significant influence for further study of the magnetars, especially for the cooling, the x-ray luminosity observation and the evolution of the magnetars.     

Charged particle motion in superstrong electromagnetic fields

The motion of charged particles in superstrong electromagnetic fields studied analytically and numerically. An analytic solution is given for constant fields which also describes satisfactorily the initial part of the motion in the slowly varying fields surrounding a pulsar.     

The generation of the highest cosmic ray energies

The acceleration of charges particles in superstrong electromagnetic fields to energies > 10²¹ eV has been studied numerically, taking into account radiation reaction effects.     

Measuring magnetic fields in plasmas by means of light scattering

The theory of light scattering in plasmas containing a magnetic field yields the special case of modulated scattering spectra. The modulation frequency is governed by the field in the plasma and is equal to the electron cyclotron frequency. In this investigation magnetic fields in a plasma were determined by a laser scattering experiment. The experimental data were: electron densityn _e=10¹⁶cm^?3, electron temperatureT _e=3.2 eV, scattering angle θ=90 °, scattering parameter α=0.6, and a maximum field in the plasma of 125 kG. The spectrum measured at the maximum magnetic field was modulated with 3.6 × 10¹¹ Hz. In scattering experiments with a field reduced by about 20% the observed modulation frequency was 2.8 × 10¹¹ Hz. A thermal spectrum with a smooth profile was found when no field was present in the plasma. Applying the theory of cyclotron modulated spectra one obtains from the scattering experiment magnetic fields of 128, 100, and 0 kG. Within the experimental accuracy these values agree well with the fields determined by means of magnetic probes. Other possible interpretations of the measured deviations from thermal spectra (modulation with the plasma frequency or additional cold electron components in the plasma) are discussed, but they afford no explanation. This experiment has domonstrated that magnetic fields in plasmas can be measured locally and almost without disturbance by means of light scattering.