Localized superconductivity in the quantum-critical region of the disorder-driven superconductor-insulator transition in TiN thin films

We investigate low-temperature transport properties of thin TiN superconducting films in the vicinity of the disorder-driven superconductor-insulator transition. In a zero magnetic field, we find an extremely sharp separation between superconducting and insulating phases, evidencing a direct superconductor-insulator transition without an intermediate metallic phase. At moderate temperatures, in the insulating films we reveal thermally activated conductivity with the magnetic field-dependent activation energy. At very low temperatures, we observe a zero-conductivity state, which is destroyed at some depinning threshold voltage V{T}. These findings indicate the formation of a distinct collective state of the localized Cooper pairs in the critical region at both sides of the transition.     

Cluster-enhanced X-O2 photochemistry (X=CH3I, C3H6, C6H12, and Xe)

The effect of a local environment on the photodissociation of molecular oxygen is investigated in the van der Waals complex X-O(2) (X=CH(3)I, C(3)H(6), C(6)H(12), and Xe). A single laser operating at wavelengths around 226 nm is used for both photodissociation of the van der Waals complex and simultaneous detection of the O((3)P(J),J=2,1,0) atom photoproduct via (2+1) resonance enhanced multiphoton ionization. The kinetic energy distribution (KED) and angular anisotropy of the product O atom recoil in this dissociation are measured using the velocity map imaging technique configured for either full ("crush") or partial ("slice") detection of the three-dimensional O((3)P(J)) atom product Newton sphere. The measured KED and angular anisotropy reveal a distinct difference in the mechanism of O atom generation from an X-O(2) complex compared to a free O(2) molecule. The authors identify two one-photon excitation pathways, the relative importance of which depends on IPx, the ionization potential of the X partner. One pathway, observed for all complexes independent of IPx, involves a direct transition to the perturbed covalent state X-O(2)(A'(3)Delta(u)) with excitation localized on the O(2) subunit. The predominantly perpendicular character of this channel relative to the laser polarization detection, together with data on the structure of the complex, allows us to confirm that X partner induced admixing of an X(+)-O(2) (-) charge transfer (CT) state is the perturbing factor resulting in the well-known enhancement of photoabsorption within the Herzberg continuum of molecular oxygen. The second excitation pathway, observed for X-O(2) complexes with X=CH(3)I and C(3)H(6), involves direct excitation into the (3)(X(+)-O(2) (-)) CT state of the complex. The subsequent photodissociation of this CT state by the same laser pulse gives rise to the superoxide anion O(2) (-), which then photodissociates, providing fast (0.69 eV) O atoms with a parallel image pattern. Products from the photodissociation of singlet oxygen O(2)(b (1)Sigma(g) (+)) are also observed when the CH(3)I-O(2) complex was irradiated. Potential energy surfaces (PES) for the ground and relevant excited states of the X-O(2) complex have been constructed for CH(3)I-O(2) using the results of CASSCF calculations for the ground and CT states of the complex as well as literature data on PES of the subunits. These model potential energy surfaces allowed us to interpret all of the observed O((3)P(J)) atom production channels.     

Determination of Alkali and Alkaline-Earth Elements in Table Salt and Sodium Chloride by Sonoluminescence

The application of sonoluminescence to the determination of sodium, calcium, and magnesium in table salt and sodium chloride solutions is studied. It is shown that the analytical performance of the procedure proposed for the determination of sodium in sodium chloride, rock salt, and vacuum-evaporated salt solutions is better than that of the known methods, in particular, atomic absorption spectrometry. This is because the proposed procedure does not require substantial sample dilution. Calcium and magnesium in these samples can be determined with satisfactory analytical performance at concentrations higher than 10 g/L.     

Use of Ultrasound in Sample Preparation for the Determination of Mercury Species by Cold-Vapor Atomic Absorption Spectrometry

Ultrasound was used for the intensification of sample preparation in the determination of different mercury species in brines and solutions of sodium chloride and common salt. Procedures were proposed for the determination of total mercury and inorganic, organic, and methyl mercury species.     

Sonoluminescent Spectroscopy in the Determination of the Major Substance of Highly Concentrated Technological Solutions

Journal of Applied Spectroscopy - The dependences of the sonoluminescence intensity of cesium, lithium, and sodium in aqueous solutions of their salts at concentrations of 400–600 g/L on the...     

A theoretical study of a special detonation regime of operation of a pulse detonation device with a variable cross section detonation combustion chamber and a valveless supply system

The results of a theoretical study of the special detonation regime that arises in a pulse detonation device with a variable cross section combustion chamber are presented. The problem is solved analytically within the framework of the one-dimensional approximation. In contrast to the standard version of arbitrary discontinuity disintegration, the problem is solved for a variable cross section at the location of the diaphragm. Since the pulse detonation device operated with a valveless system of fuel and oxidizer supply, a fuel flowed through it over the entire period before spark ignition. This peculiarity of the operation of the combustion chamber was also taken into account. The proposed approach was used to perform calculations for methane-oxygen mixtures, for which extensive experimental data exist. The calculation results are compared to the available experimental data.     

An experimental study of the diffusion-controlled self-ignition of hydrogen in a channel

The pulsed outflow of hydrogen into channels of circular and rectangular cross sections with a surface area of 20 mm² was experimentally studied. It was revealed that the shock wave formed during the outflow of a pulsed jet is the reason why it ignites at the contact surface. The range of initial pressures of hydrogen at which it ignites was determined and the dependence of the distance from the diaphragm at which a flame arises at the contact surface on the pressure in the shock wave front for circular and rectangular cross section channels was obtained.     

An increase in the sensitivity of the saturated absorption method in the multimode regime

A possibility for an increase in the signal-to-noise ratio in the laser spectroscopy that is free of Doppler broadening and is based on the saturated absorption is considered. The application of the counter-propagating laser beams in the multimode regime is proposed. The number of atoms that effectively interact with the field, and, hence, the intensity of a narrow resonance in the line shape can be increased due to the interaction of the counterpropagating modes with different frequencies. It is demonstrated that, for the intrinsic photon noise, the signal-to-noise ratio can be increased by a factor of √N, where N is the number of modes. For the remaining noises (fluctuations of the radiation power, noise of photodetector, etc.), the signal-to-noise ratio can be increased by a factor of N.