Structural and magnetic studies on RPtIn deuterides (R=Tb,Er, Tm)

In this communication, structural and magnetic properties of RPtInD_1.3 (R=Tb, Er, Tm) deuterides are reported. For the first time deuterium-rich compounds were synthesized for the RPtIn family. The investigated deuterides crystallize with the hexagonal ZrNiAl-type crystal structure, with slightly different lattice constants with respect to the basic compounds. In general, the a-lattice constant exhibit contraction, while the c-lattice constant tends to increase upon introducing deuterium. The compounds with Tb and Er shows magnetic ordering at 95 K and 15.5 K, respectively. On the other hand, for Tm based sample no magnetic ordering was evidenced down to 2 K.     

DFT simulations, FT-IR, FT-raman, and FT-NMR spectra of 4-(4-chlorophenyl)-1H-imidazole molecules

The FT-IR, FT-Raman and FT-NMR spectra of the compound 4-(4-Chlorophenyl)-1H-imidazole (4-ClPI) was recorded and analyzed. Density functional method has been used to compute optimized geometry, vibrational wavenumbers and NMR spectra of the 4-ClPI. Only one tautomeric form was found most stable by using B3LYP functional with the 6?C311++G(d,p) as basis sets. The detailed interpretation of the vibrational spectra was carried out with the aid of total energy distribution (TED) following the scaled quantum mechanical force field methodology.     

The Δk = ±2 perturbation-allowed ν4 band and inversion-rotation energy levels of 15NH3

More than 800 Δk = ±2 and 60 Δk = ±3 forbidden transitions to the ν₄ and 2ν₂ vibrational levels, respectively, have been assigned in the Fourier transform spectra of ¹⁵NH₃, recorded with a pathlength of 96 m. Combination differences derived from these transitions provide information on the spacing between the ground state energy levels with different rotational quantum numbers K in the interval from 0 to 16. These data along with wavenumbers of all the available allowed transitions pertaining to the ground and ν₂ states have been subjected to a simultaneous least-squares analysis using two different parametrization models to obtain precise values of the inversion-rotation energy levels.     

On the low-temperature properties of

Magnetic, electrical transport and heat capacity measurements have been performed on polycrystalline sample of the compound TmRu₂Si₂, which crystallizes with the tetragonal ThCr₂Si₂-type crystal structure. The results show paramagnetic behaviour down to 0.3 K, at variance with the literature data. On the basis of the collected data, possible origins of non-magnetic behaviour are discussed. Mixed valence of Tm ions or hybridisation between Tm 4f and Ru 4d states are the most probable reasons for paramagnetic behaviour of the TmRu₂Si₂.     

Isopiestic determination of the osmotic and activity coefficients of the {yKCl + (1 − y)K2HPO4}(aq) system at T = 298.15 K

The osmotic coefficients of aqueous mixtures of KCl and K₂HPO₄ have been measured at T = (298.15 ± 0.01) K by the isopiestic vapor pressure method over the range of ionic strengths from (2.3700 to 11.250) mol · kg⁻¹ using CaCl₂(aq) as the reference solution. Our new experimental results were modeled with an extended form of Pitzer’s ion-interaction model equations, both with the usual mixing terms and with Scatchard’s neutral–electrolyte mixing terms, and with the Clegg–Pitzer–Brimblecombe equations based on the mole-fraction-composition scale. There is a dearth of previously published isopiestic data for mixtures containing salts of and, consequently, no previous measurements are available for comparison with the present results. The present study yields mixing parameters for these three models that are needed for modeling the thermodynamic activities of solute components of natural waters and other complex aqueous electrolyte mixtures.     

Optical spectra of some 6-styrylo-1H-pyrazolo[3,4-b]quinolines

It was proposed a method of synthesis several 6-styrylo1-1H-pyrazolo[3,4-b]quinolines as promising material for optoelectronics. Particularly, 6-styryl-1,3-diphenyl-1H-pyrazolo[3,4-b]quinolines were prepared by Wadsworth-Emmons reaction. One of advantageous of these materials is stability of their optical spectra versus the possible cis- and trans-transformation. Theoretical and experimental studies of optical absorption and photoluminescence excitation spectra for styryloquinolines were done. They show that the AM1 semi-empirical method gives better results compared to other approaches. We have found that the solvents do not play a role in the behavior of the spectra. The backside-substituted groups do not influence substantially the observed optical spectra.     

Structure optimisation of modern GaAs-based InGaAs/GaAs quantum-dot VCSELs for optical fibre communication

Room-temperature (RT) continuous-wave (CW) performance of modern 1300-nm oxide-confined In(Ga)As/GaAs quantum-dot (QD) vertical-cavity surface-emitting diode lasers (VCSELs) taking advantage of many QD sheets is investigated using our comprehensive self-consistent simulation model to suggest their optimal design. Obviously, quantum dots should be as uniform as possible and as dense as possible to ensure high enough optical gain. Besides, our simulation reveals that efficient and uniform current injection into VCSEL active regions necessary to enhance excitation of the desired fundamental LP₀₁ mode is accomplished in the VCSEL configuration with the broad-area bottom contact and the ring upper one as well as with the oxide aperture localized within the first period of the upper p-type DBR. The doping of the DBR mirrors is chosen as a compromise between their high enough electrical conductivity and low enough free-carrier absorption. The oxide aperture is additionally introducing the radial optical waveguiding. Moreover, our analysis has been concluded that VCSEL active regions should be composed of at least 9 QD sheets to acquire efficient RT CW operation. Furthermore, rather longer optical cavities are recommended in this case because localization of QD sheets should be adjusted to the anti-node positions of the optical cavity standing wave.     

Phase time in Kane type barrier tunneling

The behavior of Wigner phase delay time in the reflection mode is studied taking into account the real band structure of Kane type semiconductor quantum ring. It's calculated the analytical expression for the saturated delay time. It's shown that the saturated delay time is independent of the width of the opaque barrier.     

Quantum correlations of spin-1 atoms in an optical lattice

In this work, we investigate the system of cold spin-1 atoms in a one dimensional optical lattice in relation with squeezing and entanglement. By using the corresponding Bose-Hubbard Hamiltonian, both superfluid and Mott-insulator phases are studied by using numerical methods in the mean-field approximation. To observe the presence of entanglement, we used a squeezing measure as a criterion for quantum correlations. We further investigate the two interaction regimes, namely ferromagnetic and antiferromagnetic in the case of zero and nonzero but very small angle between the counterpropagating laser beams that form the optical lattice. States in the superfluid phase are calculated analytically by using the perturbation theory.