Vibrational energy storage in high pressure mixtures of diatomic molecules

CO/N₂, CO/Ar/O₂, and CO/N₂/O₂ gas mixtures are optically pumped using a continuous wave CO laser. Carbon monoxide molecules absorb the laser radiation and transfer energy to nitrogen and oxygen by vibration–vibration energy exchange. Infrared emission and spontaneous Raman spectroscopy are used for diagnostics of optically pumped gases. The experiments demonstrate that strong vibrational disequilibrium can be sustained in diatomic gas mixtures at pressures up to 1 atm, with only a few Watts laser power available. At these conditions, measured first level vibrational temperatures of diatomic species are in the range T_V=1900–2300 K for N₂, T_V=2600–3800 K for CO, and T_V=2200–2800 K for O₂. The translational–rotational temperature of the gases does not exceed T=700 K. Line-of-sight averaged CO vibrational level populations up to v=40 are inferred from infrared emission spectra. Vibrational level populations of CO (v=0–8), N₂ (v=0–4), and O₂ (v=0–8) near the axis of the focused CO laser beam are inferred from the Raman spectra of these species. The results demonstrate a possibility of sustaining stable nonequilibrium plasmas in atmospheric pressure air seeded with a few percent of carbon monoxide. The obtained experimental data are compared with modeling calculations that incorporate both major processes of molecular energy transfer and diffusion of vibrationally excited species across the spatially nonuniform excitation region, showing reasonably good agreement.     

Adsorption of naphthalene on bismuth electrode from ethanol

Adsorption of naphthalene on a polarized bismuth electrode was studied from the ethanolic solutions of LiClO₄ by means of differential capacity measurements. Two regions of adsorption of naphthalene (13.2 and ?1.3 μC cm^?2) corresponding to different orientations of naphthalene molecules at the electrode surface were discovered. A sharp capacity maximum at far positive charges indicates that formation of a polymolecular adsorption layer consisting of the adsorbed naphthalene molecules in flat orientation occurs. By use of the Gibbs equation and of double layer theory the surface excess of naphthalene, adsorption energy, potential drop across the inner layer and some other adsorption parameters have been calculated for a wide range of charges. The π-oribital interaction energy of naphthalene with the bismuth surface has been estimated for various charges. A comparison of the adsorption behaviour of naphthalene in ethanolic and aqueous solutions was made.     

Magnetic-field-induced lattice anomaly inside the superconducting state of CeCoIn5: anisotropic evidence of the possible Fulde-Ferrell-Larkin-Ovchinnikov state

We report high magnetic field linear magnetostriction experiments on CeCoIn5 single crystals. Two features are remarkable: (i) a sharp discontinuity in all the crystallographic axes associated with the upper superconducting critical field B(c2) that becomes less pronounced as the temperature increases and (ii) a distinctive second orderlike feature observed only along the c axis in the high field (10 T < or approximately B< or = B(c2)) low temperature (T < or approximately 0.35 K) region. This second order transition is observed only when the magnetic field lies within 20 degrees of the ab planes and there is no signature of it above B(c2), which raises questions regarding its interpretation as a field induced magnetically ordered phase. Good agreement with previous results suggests that this anomaly is related to the transition to a possible Fulde-Ferrel-Larkin-Ovchinnikov superconducting state.     

The growth of single crystal silver wires at the nitrobenzene|water interface

Single crystal silver wires can be grown at the nitrobenzene|water interface when silver ions dissolved in the aqueous phase are reduced by decamethyl ferrocene dissolved in the nitrobenzene phase. The successful growth of these wires depends on a number of experimental conditions, most prominently on the concentration ratio of reactants, nucleation rates, shape of formed nuclei, and wettability of nuclei. The size-time dependence can be modeled on the basis of microelectrode behavior of the silver nuclei and wire. AFM, SEM, light microscopy and single crystal X-ray diffraction has been applied to study the morphology of the silver nuclei and wires.     

Band alignment at sputtered ZnSx O1–x/Cu(In,Ga)(Se,S)2 heterojunctions

Valence band offsets ΔE_VBM at ZnS_x O_1–x/Cu(In,Ga)(Se,S)₂ (CIGSSe) heterojunctions have been studied by photoemission spectroscopy (XPS, UPS) as a function of composition x in sputtered ZnS_x O_1–x films. In the composition range from ZnO to ZnS we found ΔE_VBM between –(2.1 ± 0.3) eV and –(0.8 ± 0.4) eV, respectively. Considering the optical band gaps, the conduction band offsets ΔE_CBM range from –(0.1 ± 0.3) eV to +(1.4 ± 0.4) eV. These results suggest that sputtered ZnS_x O_1–x is suitable as substitution for the CdS buffer and ZnO window layers in standard chalcopyrite‐based solar cells. Current–voltage characteristics of the solar cells have been investigated as a function of the composition x. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Modal dispersion due to photon–plasmon coupling in a SNOM tip

The mesoscopic effect of spectral modulation is used to experimentally investigate the possible effect of a metal-coated SNOM tip on the intermodal dispersion of an optical fiber. Highly regular modulation registered in a fixed spectral region of the broadband light transmitted by a 200 nm SNOM tip yields the value of optical path difference (OPD) in the two-mode model. To investigate the origin of this OPD a series of spectral measurements accompanied with a gradual reduction of the multimode fiber tail length has been performed. The results indicate that the observed OPD consists of two clearly distinguishable contributions: the OPD in the non-coated multimode fiber and the OPD in the metal-coated SNOM tip. The first one is a result of the inherent modal dispersion of an optical fiber. A numerical consideration shows that the second one can be attributed to a mode-dependent contribution of surface plasmon polaritons: one of the two modes couples to plasmons stronger than the other one, resulting in a remarkably slower propagation. This leads to a completely different value of intermodal dispersion, which actually changes its sign in the SNOM tip. Proposed is a logical explanation for such kind of a sign-switching behavior.     

Flow boiling visualization in a vertical circular minichannel at high vapor quality

This paper reports on an experimental study of saturated flow boiling of R134a inside a circular vertical quartz tube coated with a transparent heater. The inner diameter of the tube was 1.33 mm and the heated length 235.5 mm. The flow pattern at high vapor qualities and the dryout of the liquid film were studied using a high speed CCD camera at the mass fluxes 47.4 and 124.4 kg/m² s in up flow at 6.425 bar. The heat fluxes ranged from 5 to 13.6 kW/m² for the lower mass flux and from 20 to 32.4 kW/m² for the higher mass flux.

The behavior of the flow close to dryout was found to be different at low and high mass flux. At low mass flux the location of the liquid front fluctuated with waves passing high up in the tube. In between the waves, a thin film was formed, slowly evaporating without breaking up.

At high mass flux the location of the liquid front was more stable. In this case the liquid film was seen to break up into liquid streams and dry zones on the tube wall.