Optics and Spectroscopy最新文献

The splitting of the transition from a discrete to an autoionization state, used in a three-step photoionization scheme of lutetium 5d6s^2 2D_3/2–5d6s6p ({}^{4}F_{{5/2}}^{^circ })–5d6s7s ⁴D_3/2–(53375 cm^–1)(_{{1/2}}^{^circ }) has been studied. The splitting is proportional to the square root of the intensity, which corresponds to the Autler–Townes effect.

In this work, copper-doped carbon nanoparticles with emission in a wide spectral range and the ability to change the relaxation times of water protons during magnetic resonance imaging were fabricated. A high relaxivity value r1 = 0.92 mM^–1 s^–1 was achieved, which is the highest value of r1 for copper nanoparticles, to our knowledge. The suggested carbon nanoparticles are promising two-modal nanoprobes for bioimaging.

Numerical modeling of multilayer piezoactuators with a cross-sectional area of 2 × 2 mm was carried out. It was shown that when interdigitated switching is used in piezoactuators, a local redistribution of transverse strain maxima is observed, which leads to a decrease in the mechanical strength and reliability of control elements. Piezoceramic combs with identical linear dimensions were produced and the mechanical and electrical properties of the developed elements were measured. It was revealed that stroke at a control voltage of 300 V decreases from 4 to 1.5 μm when using the interdigitated switching method in comparison with multilayer actuators of larger cross-section due to a decrease in the effective polarization area of piezoactuators. Piezoceramic combs with wire commutation were manufactured, where the displacement at a control voltage of 300 V was 4.6–4.8 μm.

The presence of the orbital collapse of the g-orbitals in the excited state of the atom with the nuclear charge number Z = 124 and in the ground state of the atom with Z = 125, which belong to the 8th period of the extended periodic table, is demonstrated. In both cases, the orbital collapse occurs within the same configuration when increasing the total angular momentum J, which characterizes the relativistic term of the atom in the jj coupling. All calculations are performed by means of the relativistic Dirac–Fock method.

The most important parameter determining the efficiency of carbon dots as light absorbers in photocatalytic systems is the strength of their binding to the catalyst. It is rather difficult to estimate the contribution of this parameter of carbon dots to the overall efficiency of the photocatalytic system, since the post-synthetic modification of the surface of carbon dots is accompanied by a significant change in their optical and structural properties. In this work, we performed post-synthetic modification of the surface of carbon dots based on citric acid by amination with ethylenediamine molecules by activating the carboxyl groups of carbon dots with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide molecules. The use of this amination approach made it possible to change the charge of carbon dots without changing their main optical and structural properties, which can be further used to assess the contribution of the strength of their binding with Dubois-type molecular catalysts to the overall efficiency of the photocatalytic system.

Optical properties of an inhomogeneous ensemble of plasmonic silver nanoparticles obtained by thermal vacuum deposition at the interface between two media as this interface moves relative to the nanoparticles themselves have been studied. The movement was carried out due to thermally stimulated diffusion of nanoparticles into the polystyrene layer and due to the deposition of an additional layer of quartz on a granular film with nanoparticles on a quartz substrate. The frequency shifts of the inhomogeneous plasmon resonance of nanoparticles moving through the interface was to about two tens of nanometers.

The results of laboratory measurements of the transparency of fresh ice blocks in the optical range in the temperature range from –15 to 0°C are presented. The studies were performed at two wavelengths in the visible range (at a wavelength of 535 nm) and the ultraviolet range (at a wavelength of 370 nm). We studied the ice of a natural fresh water body with a characteristic predominant spatial orientation of the main optical axis of the crystals. It has been established that when approaching a temperature of 0°, the sample becomes bleaching (decrease in attenuation). The effect occurs in the range –0.5–0°C. It is determined by the occurrence of plastic deformation due to thermal stresses caused by the initial stage of the ice-water phase transition. The bleaching in experiments with ice blocks ~10 cm thick was 3–25%. The results obtained are of interest for solving remote sensing problems, since melting ice is a widespread object due to its significant heat of phase transition. Previously, the effect of bleaching of fresh ice was also discovered in the microwave range when the temperature of the sample approached the phase transition point.

The quantum vortices formed as a result of barrier-suppression ionization of a two-dimensional hydrogen atom by an ultrashort laser pulse are theoretically investigated. Using an analytical expression for the wave function of a photoelectron in the momentum representation, the probability flux density is investigated. In this case, both the standard definition of a flux and an alternative “symmetrical” one are used. The latter, due to the sensitivity to the phase of the wave function, makes it possible to identify quantum vortices in the momentum space.

One-dimensional photonic crystals with an arbitrary number and spectral position of photonic band gaps in the optical spectral range are experimentally demonstrated. The absence of mutual influence of the photonic band gaps was shown. No features corresponding to higher harmonics or combination frequencies were found in the spectral response of the multifrequency photonic crystals created.

When excited by a powerful picosecond pulse of the second harmonic of a YAP:Nd laser, inelastic scattering lines with frequency detunings in the range of  ~10–130 GHz relative to the laser line were detected in suspensions of morphologically similar AltMV and PVX viruses. This scattering has a threshold nature, and the sets of its spectral lines are different for different virus samples.