JETP Letters最新文献

Formulas to calculate the atomic photoionization delay have been derived taking into account the interaction between the channels and the scattering of a photoelectron. The photoionization delay difference between Ne 2p and 2s shells has been calculated for photon energies up to 200 eV. The calculated delay difference at a photon energy of 105 eV is 18.5 as, which is approximately 8 as larger than delay differences previously calculated taking into account only the interactions between the channels and is in agreement within the experimental error with two existing experimental values.

Sulfide composites ZnS/Ag₂S with various contents of silver sulfide have been synthesized by chemical co‑deposition. The sizes of ZnS and Ag₂S nanoparticles in ZnS/Ag₂S composites containing less than 1.0 mol % Ag₂S are ~4 and <3 nm, respectively. The introduction of silver sulfide in ZnS/Ag₂S composites leads to the deposition of Ag₂S on the surface of ZnS nanoparticles. The doping of ZnS nanoparticles by only 1 mol % Ag₂S nanoparticles is enough to form a covering silver sulfide shell on the surface of ZnS nanoparticles.

We present the experimental study of free-space optical control of the optical beam phase shift caused by the formation of a layered structure in an elementary controllable cell made of phase-change material Ge₂Sb₂Te₅ subjected to the controlling effect of pulsed laser radiation. The phase change of the signal optical beam passing through the controlled cell from phase-change material relative to the control beam in the Jamin interferometer is demonstrated.

Energy transfer is investigated in coupled planar magnon “ferromagnet–normal metal” heterostructures with equivalent amplification and damping of spin waves, in which an exceptional point (point in the space of the parameters of a system where its eigenvalues and eigenvectors degenerate) can be observed. It is shown that an increase in the direct current of different polarities (causing a change in the spin-polarized current) leads to an increase in the length of energy transfer from one heterostructure to another, which tends to infinity at the exceptional point. The mismatch in the natural magnetization damping constants of the two waveguides reduces the critical current at which the exceptional point arises, whereas the mismatch in the wavenumbers (the absence of phase-velocity synchronism) increases the critical current at a bounded energy transfer length. The results presented can be used to design controlled magnon directional interconnects.

The formation of craters with the characteristics varying in the longitudinal and transverse directions at the laser microperforation of dielectric materials faces significant problems. In this work, a method have been proposed for the microstructuring of polystyrene as an example of polymeric materials involving laser photonic hooks and a low-cost cw laser. An optical fiber with an asymmetric conical tip has been used to form a photonic hook. Experiments demonstrate that curved microcraters with a shape depending on the power of laser radiation can be formed in a polymer substrate.

It has been shown numerically that coupled nonlinear Schrödinger equations describing the interaction between the left and right circular polarizations of a paraxial optical wave in a defocusing Kerr medium with an anomalous dispersion in a helical waveguide have stable solutions in the form of elongated stationary rotating bubbles with several optical vortices attached to the ends. A bubble is an arbitrarily long quasi-cylindrical three-dimensional cavity in one of the components filled with the opposite component. The transverse profile of the bubble is determined by the shape of the cross section of the waveguide, the helix pitch, the number of vortices, and the background intensity of the surrounding component rather than by the total amount of the filling component.

Synchronous spatiotemporal measurements of hard X rays emitted during the development of a high-voltage discharge at voltages of ~1 MV in half-meter open air gaps have been carried out for the first time. Using an array of scintillation detectors with lead diaphragms and the nanosecond photography of the discharge in the intrinsic luminescence, it has been shown that X rays are emitted in the discharge development stage when numerous brightly luminescent plasma channels are formed in the entire discharge gap and the discharge current with an amplitude of hundreds of amperes flows. It has been found that the emission of X rays (photons with energies above 5 keV) can start almost synchronously in the entire discharge gap, including the cathode and anode regions, near-cathode and near-anode regions, and the middle of the discharge gap. The statistical distributions of the total power and the number of the observed X-ray flashes along the discharge gap have been obtained.

Transient processes in the photoconductivity of TiS₃ single crystals exposed to rectangular light pulses in the wavelength range of λ = 405–940 nm are investigated. It is established that the decay in the photoconductivity after switching the light off at temperatures from 78 to 180 K is described by a logarithmic law in the range from 10^–3 to 10² s (i.e., when time changes by five orders of magnitude). This means that the relaxation process is characterized by times ranging, at least, from several tens of microseconds to several tens of minutes. It is shown that the relaxation is basically successive: the recombination barrier increases while the conductivity approaches the equilibrium value.

It is shown that electromagnetic interactions of cosmic ray protons provide a noticeable contribution to positrons production. This is due to a combination of low energy threshold of electron–positron pair creation compared to the thresholds of pion creation in strong interactions and rapid decrease of the cosmic rays energy spectrum. Moreover, the electromagnetically produced positrons are very soft, therefore their annihilation with background electrons directly produces the observed 511 keV gamma-line.

A method of the transfer of NaYF₄:Yb³⁺Tm³⁺/NaYF₄ upconversion core/shell nanoparticles with an average size of 30 nm via laser-induced forward transfer is proposed. The method provides a high spatial resolution by creating a “sandwich” structure on the donor substrate: for reliable fixation, nanoparticles are located between gold layers 50 and 20 nm thick. The transfer of upconversion nanoparticles is implemented by focusing nanosecond laser radiation into a 30-μm-diameter spot and at optimal pulse energies of 8.5–25 μJ. It has been shown that, despite large temperature, (Delta T > 1000{kern 1pt} ) K, and pressure, (Delta P > 150{kern 1pt} ) MPa, fluctuations upconversion nanoparticles fully retain their photoluminescent characteristics.