The color centers in nanodiamonds are promising candidates for the fabrication of stable room-temperature sources of single photons. We investigate the luminescent and morphological properties of ...milled high-pressure high-temperature nitrogen-vacancy (NV) center nanodiamonds with sizes of
∼
10 – 160 nm on a glass substrate. We carry out the studies of photoluminescence and Raman spectra of a nanodiamond powder under excitation at wavelength
⋋
0
= 532 nm and demonstrate the presence of luminescence of NV
−
and NV
0
centers, as well as fundamental diamond Raman peak (1332 cm
−
1
). Laser scanning confocal fluorescence microscope images of NV centers under 532 nm CW excitation show the single-emitter behavior of these centers. The second-order correlation functions
g
(2)
(t) for one or several (2–4) emitting NV centers are measured. We receive minimum
g
(2)
(0) = 0
.
15 with background correction and estimate the photoluminescence lifetimes of NV centers from 10 to 25 ns. For a single NV center, we obtain the saturation count rate of
∼
250 kcounts/s.
Interview with a leading expert in the treatment of gout, head of the laboratory of microcrystalline arthritis of the Federal State Budget Scientific Institution “Scientific Research Institute of ...Rheumatology named after V.A. Nasonova“ candidate of medical sciences Maxim Sergeevich Eliseev.
The paper considers a concept of feedbacks in the dynamics of mechanical oscillation systems. The authors propose a generalized theory of dynamic damping of oscillations as a process of introducing ...additional constraints in a basic model that looks like a system with one or two degrees of freedom. This article describes a method for constructing mathematical models and the results of studying the features of the dynamic properties of systems in which dynamic oscillation damping modes can be implemented.
Research on the optical parameters of the plasma of a nanosecond capillary discharge in a gas mixture of argon and helium was presented in the spectral range of 2–10 nm. Dependences of the intensity ...of the glow of the emission spectra of the plasma on the gas pressure are obtained, and the possibility of obtaining a soft X-ray beam with a low divergence is shown.
The methodological basis of constructing mathematical models of vibratory technological machines is developed in the article. An approach is proposed that makes it possible to introduce a vibration ...table in a specific mode that provides conditions for the dynamic damping of oscillations for the zone of placement of a vibration exciter while providing specified vibration parameters in the working zone of the vibration table. The aim of the work is to develop methods of mathematical modeling, oriented to technological processes with long cycles. The technologies of structural mathematical modeling are used with structural schemes, transfer functions and amplitude-frequency characteristics. The concept of the work is to test the possibilities of combining the conditions for reducing loads with working components of a vibration exciter while simultaneously maintaining sufficiently wide limits in variating the parameters of the vibrational field.
In this work, we studied the photon echo from heavy-hole excitons in a thin InGaAs/GaAs quantum well. To analyze the results, we used the model of an ensemble of two-level systems. The model allows ...us to describe the temporal profile and the moment of arrival of the echo signal, as well as the echo amplitude decay with increasing delay between pulses. In addition, excitation-induced dephasing effect was observed, that was beyond the limits of applicability of the model.
Creating stable and efficient compact X-ray sources based on fast capillary discharges that do not incorporate preliminary ionization circuits poses additional restrictions on parameters of voltage ...pulses and capillary geometry. Applying a voltage pulse with a rise rate of the order of 1 kV/ns results in gradual breakdown of non-ionized gas in the capillary which takes the form of an ionization wave that initiates at the powered electrode and propagates with typical velocities of 1 cm/ns. After the wave reaches the grounded electrode, a plasma channel with gradually increasing conductivity is formed. The current onset therefore appears only after a certain time delay after beginning of the voltage pulse. The ratio between the delay and the applied voltage rise-time will eventually influence the current rise rate that defines plasma heating and compression. It is therefore necessary to have the ability to estimate this delay time for a given capillary geometry and understand its dependence on the properties of a voltage pulse. In this work numerical simulations of fast ionization waves created in an extended Al2O3 capillary filled with nitrogen at 2 Torr were performed for cases of voltage pulses of negative polarity with rise-times varying in the range 10-50 ns. The numerical model was based on fluid approach with drift-diffusion approximation for charged particle fluxes. Influence of voltage rise-time on initiation and propagation of a fast ionization wave as well as on consequent rate of current rise is investigated.
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