Bulletin of the Lebedev Physics Institute最新文献

The advantages and shortcomings of two-photon laser lithography (TPL) technology for fabricating X-ray compound refractive lenses (CRLs) are discussed. A CRL consisting of 15 one-dimensional refractive lenses with an aperture of 185 µm was fabricated and then tested at the “Microfocus” beamline (KISI-Kurchatov) for photon energies of 8 and 12 keV. Factors affecting the focal spot size and focal length are discussed. TPL technology provides acceptable surface roughness of the lenses and the required radius of curvature, but the lenses are inhomogeneous internally due to the presence of uncured photocurable composition in the gaps between polymerized areas. This inhomogeneity is one of the reasons for the broadening of the focal spot, as well as undesirable effects of synchrotron radiation (SR). The combination of TPL and nanoimprint technology is proposed, which would simultaneously preserve the best characteristics of the lenses and eliminate the disadvantages of the TPL method.

The paper examines a high-voltage, pulsed-periodic surface discharge propagating along a water‒gas interface using argon and oxygen as the gas medium. In the experiments, use is made of a generator with a storage capacitor energy of 1.6 J, a voltage of 20 kV, and a pulse duration of 2–3 μs. The discharge channel length is varied in the range from 3 to 15 cm. The average velocity of discharge propagation along the water surface in an Ar and O₂ atmosphere is determined. The leader velocity in argon is shown to be twice that in oxygen. Hydrogen peroxide synthesized in liquid under the action of the discharge is quantitatively measured. It is found that hydrogen peroxide production linearly depends on the discharge channel length in the range from 3 to 9 cm, both when using argon and oxygen as the working gas.

Upon focusing pulsed laser radiation into pure liquids, solutions, and colloidal solutions, an increase in the duration of the laser pulse passing through a cuvette with a sample is detected. The increase in duration probably stems from the formation of negative feedback due to stimulated scattering.

This study investigates the effect of hydrogen exposure on magnetron-sputtered films of platinum group metals (Pd, Au/Pd, and Pt) with thicknesses ranging from 25 to 350 nm. The films were characterized using optical spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. Their electrical resistance was measured by the four-probe method. The results of studying the interaction of hydrogen with Pd, Au/Pd, and Pt reveal differences in their reactivity, including active reduction of PdO in palladium, moderate absorption in platinum, and stability of composite Au/Pd films. These study findings have significant potential for the development of hydrogen sensors and catalysts.

We report a numerical investigation of the characteristics of a cumulative jet formed by the collapse of a vapor bubble at the end of a thin (~0.6 mm) fiber during laser-induced subcooled boiling in the presence of a liquid flow directed along the fiber axis. Flows in both directions are considered. Data on the dependence of the jet velocity on the that of the liquid flow are obtained. It is shown that there is a range of flow velocities beyond which jet formation is impossible. Analysis of the dynamics of vapor bubble growth and collapse makes it possible to explain the reasons for the impossibility of jet formation at high absolute values of the flow velocity.

The study investigated the effectiveness of wound healing in laboratory mice after a single application of silver and copper nanoparticles. The wounds were infected with a mixed bacterial culture of Staphylococcus aureus and Pseudomonas aeruginosa. Wound healing was assessed using planimetry and microbiological culture methods.

We propose and experimentally demonstrate the possibility of efficient lasing at the C³Π_u–B³Π_g transition of the N₂ molecule in the afterglow of a high-pressure Ar–N₂–He mixture excited by an electron beam with an average electron energy ε_e ≈ 300 keV, an average current density j ≈ 30 A/cm², and a FWHM duration τ ≈ 100 ns. With a laser pulse duration of ∼110 ns, the laser energy is ∼65 mJ.

We report the results of numerical simulations of the generation of low-frequency Alfvén waves generated by periodic laser plasma bunches in a partially ionized background plasma. The effect of neutral particles on the structure, intensity, and velocity of the disturbances, as well as their maximum content in the plasma, are considered.

We consider a communication line without dispersion compensation. The pulse-broadening rate and the distance at which stationary signal power statistics are established are estimated. It is shown that the probability of exceeding a given power level decreases exponentially with increasing level.

For the boson sampling problem, a validation method is proposed based on the analysis of the space of measured Fock states expressed as strings of non-negative integers. The method is based on introducing a radial function ({{G}_{{{{p}_{0}}}}})(r) in the space of such strings with an l₁-metric. The function ({{G}_{{{{p}_{0}}}}})(r) depends on the internal structure of the collected statistics for strings of integers and will therefore differ significantly for different samplers. The method is tested for samplers with Fock, coherent, and thermal states, as well as for distinguishable particles in the nonunit quantum efficiency regime of the measuring photodetectors. It is shown that for a photon loss probability p_loss ≤ 0.1 at the photodetector, the radial function of a sampler with Fock states is qualitatively different from that of samplers with coherent and thermal states. Knowledge of ({{G}_{{{{p}_{0}}}}})(r) in this case is sufficient to qualitatively distinguish a boson sampler from those described above. For p_loss ≥ 0.2, the radial functions of the Fock, thermal, and coherent samplers may be superficially similar. Validation in this case is only possible if, in addition to the radial function, the p_loss value is known. A statistical test is used for validation. The radial functions ({{G}_{{{{p}_{0}}}}})(r) of a Fock sampler and a sampler with distinguishable particles are qualitatively indistinguishable for any p_loss loss level. Therefore, p_loss must be known to statistically distinguish these samplers.