Optics and Spectroscopy最新文献

In this work, the spectra of optical constants of epitaxial layers of cadmium telluride near the fundamental absorption edge are studied. For this purpose, ellipsometric measurements of the layers under study were carried out in a vacuum chamber in the temperature range from T = 38–275°C. A numerical algorithm has been developed for solving the inverse ellipsometry problem for the structures under consideration, with the help of which the spectral dependences of the refractive index n(λ) and absorption index k(λ) are determined in the wavelength range from 700 to 1000 nm. The parametric dependences of k(λ, T) in the fundamental absorption region and in the transparency region are presented. The presence of an extended absorption tail in the transparency region was established, presumably associated with imperfections in the crystal structure.

An experiment was set up to study the afterglow of an extended barrier discharge in low-pressure neon containing Ne⁺, Ne²⁺, and Ne⁺⁺ ions by kinetic spectroscopy. Observation conditions: neon pressure ~0.8–1.7 Torr, electron density in the afterglow stage [e] ~ 10¹¹ cm^–3. In order to compare the rates of collisional-radiative recombination of Ne⁺ and Ne⁺⁺ ions, the effect of pulsed “heating” of decaying plasma electrons by a weak high-frequency field on the intensities of atomic and ion lines was observed. The presented data show that in such a plasma, short-term suppression of recombination processes by electron heating leads to an increase in the brightness of spectral lines in the atomic and ion afterglow spectra, and the reaction of the lines of the latter turns out to be much stronger. Based on simple estimates, it is shown that this effect is due to the difference in the recombination rates of the Ne⁺ and Ne⁺⁺ ions, and this difference turns out to be beyond the scope of theoretical concepts.

Systematic quantum chemical calculations were performed for the ground and a number of low-lying electronically excited doublet and quartet states of the rubidium trimer molecule. The obtained potential energy surfaces (PES), spin-orbit couplings (SOC) and electronic transition dipole moments (ETDM) can be useful for optimizing paths for laser synthesis, cooling and manipulation of stable ensembles of Rb₃ molecules at ultralow temperatures. Ab initio calculations of the electronic structure of the homonuclear Rb₃ molecule, in linear, isosceles triangle and equilateral triangle geometries, were performed using the multi-reference configuration interaction method, taking into account single and double excitations (M-R‑CISD) and with explicit dynamic correlation of only the three valence electrons. The structure of each atom was approximated using a nine-electron effective core potential (ECP28MDF), and molecular orbitals (MOs) were optimized using the spin averaged (over doublet and quartet states) multi-configuration self-consistent field (SA-CASSCF) method. Core–valence correlations between twenty-four subvalence electrons located on doubly occupied MOs and three valence electrons were implicitly taken into account using a one-electron angular momentum-independent Müller–Mayer core polarization potential (CPP). As a result of topological investigations at over 35 000 points, two dimensional PES, SOC, and ETDM functions were obtained and the geometric parameters Rb₃ were found at which the most intense vertical transitions and the maximum influence of the SOC are expected.

In this paper, the possibility of detecting viruses, specifically influenza A virus, based on changes in the spectra of total reflection from macroporous silicon (macro-pSi) films, is demonstrated for the first time. Macro-pSi films with a pore diameter of about 100 nm were produced by electrochemical etching of crystalline silicon substrates. The porosity of the macro-pSi, calculated using the Bruggeman effective medium model, was 75%. Electron microscopy showed that such highly porous films adsorb of 50–100 nm in size viruses on their surface and inside the pores, but the efficiency of adsorption significantly increases when the surface of the nanostructures is functionalized with monoclonal antibodies, providing specific binding of viruses. The reflection spectra of macro-pSi films demonstrate a series of interference fringes, the intensity of which dramatically changes upon virus adsorption. The results obtained demonstrate the possibility of a simple and effective optical method for virus diagnostics using Fabry–Pérot interference in macro‑pSi films.

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.