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The combination of amino acid anions with the choline cation gives origin to a new and potentially important class of organic ionic liquids that might represent a viable and bio-compatible alternative with respect to the traditional ones. We present here a detailed study of the bulk phase of the prototype system composed of the simplest amino acid (alanine) anion and the choline cation, based on ab initio and classical molecular dynamics. Theoretical findings have been validated by comparing with accurate experimental X-ray diffraction data and infrared spectra. We find that hydrogen bonding (HB) features in these systems are crucial in establishing their local geometric structure. We have also found that these HBs once formed are persistent and that the proton resides exclusively on the choline cation. In addition, we show that a classical force field description for this particular ionic liquid can be accurately performed by using a slightly modified version of the generalized AMBER force field. [ABSTRACT FROM AUTHOR]

We present here a small-scale liquid helium immersion cryostat with an innovative optical setup suitable to work in long wavelength radiation ranges and under an applied magnetic field. The cryostat is a multi-stage device with several shielding in addition to several optical stages. The system has been designed with an external liquid nitrogen boiler to reduce liquid bubbling. The optical and mechanical properties of the optical elements were calculated and optimized for the designed configuration, while the optical layout has been simulated and optimized among different configurations based on the geometry of the device. The final design has been optimized for low-noise radiation measurements of proximity junction arrays under an applied magnetic field in the wavelength range λ = 250 μm–2500 μm. [ABSTRACT FROM AUTHOR]

The infrared side bands associated with the vibrational modes of SiH4 and GeH4 have been studied in the solid phase. At low T, all of the observed bands exhibit librational transitions. The tunneling splitting EA–T has been extracted from the librational energies. It turns out to be 0.2 μeV in SiH4 II, in excellent agreement with previous nuclear magnetic resonance determinations, and about 5×10-2 μeV in GeH4 (IV). A broad but distinguishable librational absorption is still present in the plastic phases at high T. The observation of overtone and combination bands is also reported. [ABSTRACT FROM AUTHOR]

The infrared vibrational bands of solid CD4 in the ordered phases II and III have been observed, and their fine structure resolved. Evidence for the existence of free rotating molecules has been found in CD4 II. At lower temperatures, the ν4 band is well fitted by the sum of eleven lines: their number and relative intensities are consistent with a three-site model for phase III of solid methane. Overtone and combination bands up to the third order are also reported. [ABSTRACT FROM AUTHOR]

Describes the near infrared spectrum of solid silane. Observation of overtones and combination bands; Agreement between the observed overtones and local mode approach; Determination of both the harmonic and anharmonic parameters of the stretching the solid state.

The infrared absorption spectrum of solid CD4 has been studied in detail in the frequency range between 2000 and 7000 cm-1. In the three normal-pressure phases of CD4 between 30 and 2 K, 25 weak overtone and combination bands have been observed. They have been tentatively assigned on the basis of their energies, structures, and intensities. Overtones of order v4 of the bending mode ν4 have been detected for v4=2, 3, 4, 6. As v increases, one observes the transition from a regime where propagating vibrons are created on different molecules, to a regime where multivibron transitions occur on single molecules. Such behavior is triggered by changes in the intramolecular anharmonicity, which plays the role of a vibron–vibron binding energy. [ABSTRACT FROM AUTHOR]

The infrared absorption spectrum of CH4 from 4000 to 12 000 cm-1 has been first studied in the solid phases I and II. More than forty overtone and combination bands, up to the sixth order, have been observed. Some of them are weaker by a factor of ≊105 than the infrared fundamentals. The bands have been assigned on the basis of their frequency, structure, and intensity. Features that can be attributed to propagating vibrons have been observed. The rotovibrational lines of molecules at Oh sites of phase II have been resolved in a few bands, and their relative intensities are in excellent agreement with the predictions of the extended James and Keenan model. The results reported here may help to analyze more complicated spectra, as those of CH4 in planetary atmospheres. [ABSTRACT FROM AUTHOR]

Presents a study that discussed the advantages of the use of amorphous magnetic cores in power transformers for induction heating applications in the frequency 20 to 50 kilohertz. Description of the 25-kilohertz-600-kilovar transformer; Analysis of the frequency range 20 to 50 kilohertz; Conclusion.

Presents a study which examined the technical and economical problems of applying amorphous magnetic cores in medium-frequency transformers for induction heating applications. Core material characteristics; Experiments on a power transformer; Conclusion.

It was recently shown that superlattices where layers of the 8% Co-doped BaFe2As2 superconducting pnictide are intercalated with non superconducting ultrathin layers of either SrTiO3 or of oxygen-rich BaFe2As2, can be used to control flux pinning, thereby increasing critical fields and currents, without significantly affecting the critical temperature of the pristine superconducting material. However, little is known about the electron properties of these systems. Here, we investigate the electrodynamics of these superconducting pnictide superlattices in the normal and superconducting state by using infrared reflectivity, from THz to visible range. We find that multigap structure of these superlattices is preserved, whereas some significant changes are observed in their electronic structure with respect to those of the original pnictide. Our results suggest that possible attempts to further increase the flux pinning may lead to a breakdown of the pnictide superconducting properties. [ABSTRACT FROM AUTHOR]

We present a spectromicroscopy study of the two distinct metal-insulator transitions in (V1-xCrx)2O3, x = 0.011. The coexistence of metallic and insulating domains was observed with scanning photoelectron microscopy for both the paramagnetic insulator-paramagnetic metal and paramagnetic metal-antiferromagnetic insulator transitions, evidencing a clear correlation between their nucleation regions. Although these two transitions are very different in nature and underlying mechanism, in both cases the morphology of their phase separation is influenced by structural inhomogeneities. These results demonstrate the general relevance of strain caused by local lattice distortions in guiding the intrinsic tendency towards phase separation in Mott materials. [ABSTRACT FROM AUTHOR]

A midinfrared mass sensor based on high quality factor surface plasmon modes was designed, fabricated, and tested by infrared spectroscopy for the detection of nanometric layers of dielectric materials. Substrate removal below a metal mesh with period of 2 μm results in the coupling between degenerate surface plasmon modes on the two surfaces, resulting in a quality factor up to 33 for the antisymmetric mode. The presented substrateless metal mesh integrates mass sensing capability together with midinfrared spectroscopy, and is therefore of potential interest for substance-selective environmental and biomedical sensing applications [ABSTRACT FROM AUTHOR]

In this letter we present the experimental evidence of intersubband absorption in the conduction band of compressively strained germanium quantum wells bounded by Ge-rich SiGe barriers. The measured absorption energies are in the terahertz range and are interpreted by means of tight binding calculations which include self-consistent band-bending and depolarization effects. From the comparison of experimental and numerical results a conduction band offset along the L line of about 120 meV has been estimated for the studied heterostructures. [ABSTRACT FROM AUTHOR]

We describe the project for the construction of a terahertz (THz) beamline to be called TeraFERMI at the seeded FERMI free electron laser (FEL) facility in Trieste, Italy. We discuss topics as the underlying scientific case, the choice of the source, the expected performance, and THz beam propagation. Through electron beam dynamics simulations we show that the installation of the THz source in the beam dump section provides a new approach for compressing the electron bunch length without affecting FEL operation. Thanks to this further compression of the FEL electron bunch, the TeraFERMI facility is expected to provide THz pulses with energies up to the mJ range during normal FEL operation. [ABSTRACT FROM AUTHOR]

The linac driven coherent THz radiation source at the SPARC-LAB test facility is able to deliver broadband THz pulses with femtosecond shaping. In addition, high peak power, narrow spectral bandwidth THz radiation can be also generated, taking advantage of advanced electron beam manipulation techniques, able to generate an adjustable train of electron bunches with a sub-picosecond length and with sub-picosecond spacing. The paper reports on the manipulation, characterization, and transport of the electron beam in the bending line transporting the beam down to the THz station, where different coherent transition radiation spectra have been measured and studied with the aim to optimize the THz radiation performances. [ABSTRACT FROM AUTHOR]