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A superconducting Fabry–Perot microwave cavity for a molecular trap was designed, constructed and characterized. The cavity was designed to create intense microwave fields that are sufficient to trap cold polar molecules by the AC Stark force. By coating the mirror surfaces with a superconducting material, an unloaded quality factor of up to 1.1 × 106 at 24.087 GHz was achieved at a temperature of 2.24 K. The field strength of 1.06 MV m−1 obtained for a TEM02 transverse mode with an input power of 10 W is sufficiently intense to trap ammonia molecules at a temperature of 85 mK, which is achievable by a conventional Stark molecular decelerator. We have also implemented an ion optics assembly for sensitive detection of molecules inside the microwave cavity by resonance enhanced multi-photon ionization.

We present a comparison of two technically distinct methods for the generation of rotationally cold, pulsed supersonic beams of methyl radicals (CH3): a plate discharge source operating in the glow regime and a dielectric barrier discharge source. The results imply that the efficiency of both sources is comparable and that molecular beams with similar translational and rotational temperatures are formed. Methane (CH4) proved to be the most suitable radical precursor species. (c) 2018 Author(s).

Presented herein is a detailed discussion of the properties of the lattice dynamic and optoelectronic properties of tantalum(V) oxynitride (TaON) and tantalum(V) nitride (Ta 3 N 5 ), from experimental and theoretical standpoint. The active Raman and infra red (IR) frequencies of TaON and Ta 3 N 5 were measured using confocal Raman and Fourier Transform Infrared spectroscopies (FTIR) and calculated using the linear response method within the density functional perturbation theory (DFPT). The detailed study leads to an exhaustive description of the spectra, including the symmetry of the vibrational modes. Electronic structures of these materials were computed using DFT within the range-separated hybrid HSE06 exchange–correlation formalism. Electronic and ionic contributions to the dielectric constant tensors of these materials were obtained from DFPT within the linear response method using the PBE functional. Furthermore, effective mass of photogenerated holes and electrons at the band edges of these compounds were computed from the electronic band structure obtained at the DFT/HSE06 level of theory. The results suggest that anisotropic nature in TaON and Ta 3 N 5 is present in terms of dielectric constant and effective masses.

We have demonstrated that a supersonic beam of methyl radicals (CH$_3$) in the ground rotational state of both $para$ and $ortho$ species has been slowed down to standstill with a magnetic molecular decelerator, and successfully captured spatially in an anti-Helmholtz magnetic trap for $>$ 1 s. The trapped CH$_3$ radicals have a mean translational temperature of about 200 mK with an estimated density of $>5.0\times10^7$ cm$^{-3}$. The methyl radical is an ideal system for the study of cold molecules not only because of its high reactivities at low temperatures, but also because further cooling below 1 mK is plausible via sympathetic cooling with ultracold atoms. The demonstrated trapping capability of methyl radicals opens up various possibilities for realizing ultracold ensembles of molecules towards Bose-Einstein condensation of polyatomic molecules and investigations of reactions governed by quantum statistics.

The equilibrium structures and bonding features of [NeHHe] + , [ArHHe] + , and [ArHNe] + are investigated using correlated ab initio methods and a large number of basis sets. For all the three systems, linear structures with the hydrogen atom in the middle have been found to be the most stable. The bond lengths of argon atoms with hydrogen are shorter than the HeH and NeH bond lengths in [ArHHe] + and [ArHNe] + , respectively. This leads to the dissociation energies being very large for breaking the heavier rare gas-hydrogen atom bond. In [NeHHe] + , the NeH bond length is larger than HeH length. In addition to the global minima, two other local minima are also located for each of the systems with either of the rare gases in the middle. All the stable geometries are characterized by frequency calculations.

The treatment of non-Newtonian fluids in tubular reactors is frequently encountered in industries, which may be studied by mathematical modeling. The modeling of endothermic reactions of non-Newtonian fluids in tubular reactors with radial dispersion has been done for Ostwald-de-Waele power law fluids. The coupled mass balance, heat balance and velocity equations have been dealt with. The model is solved using finite difference numerical methods. The effect of variation in the dimensionless parameters of the model has also been studied. In addition, the rheological parameter n also affects the reactor performance as well as the velocity profile. An increase in n leads to higher velocity distortion and a decrease in conversion and temperature.