1,721,005 research outputs found
Broadband Terahertz Spectroscopy of Imidazolium-Based Ionic Liquids
No full textIonic liquids are liquid salts at ambient temperature composed of organic cations and organic/inorganic anions. Outstanding physical and chemical properties of ionic liquids lead to increasing application in scientific and industrial field. Ionic liquids have been already investigated by different spectroscopic techniques, including terahertz (THz) time-domain spectroscopy. The usual THz frequency range extends up to 2-3 THz, a relatively narrow band, which can only show the intermolecular vibrational modes. Here, we report about broadband THz spectroscopy of ionic liquids up to 13 THz. Bandwidth of intermolecular absorption band presents an unexpected behavior and strong sharp intramolecular absorptions are shown. In addition, we found violation of the approximation of harmonic oscillator used to predict the peak shift of intermolecular absorption band
Terahertz hyper-Raman time-domain spectroscopy of gallium selenide and its application in terahertz detection
No full textWe report the observation of Terahertz (THz) hyper-Raman generation in a gallium selenide crystal. This nonlinear optical process derives from the four- and five-wave-mixing of femtosecond optical pulses and intense, subps, broadband terahertz pulses. The wavelength spectrum of the resulting signal displays two pronounced frequency sidebands close to the optical second-harmonic central frequency 2 ω L, where ωL is the optical central frequency of the fundamental beam. The two sidebands develop around the central frequency at the (anti-) Stokes side of ω s, a = 2 ω L ω T, where ωT is the THz central frequency. This nonlinear optical process is used for the coherent detection of intense and broadband terahertz waves. The proposed technique shows a good linear response of up to 90 kV/cm and a better efficiency in detecting the lowest terahertz frequencies, as compared to the standard electro-optic sampling performed in two different nonlinear crystals
Photoinduced random molecular reorientation by nonradiative energy relaxation: An experimental test
No full textLight-induced modification of kinetic molecular properties: enhancement of optical Kerr effect in absorbing liquids, photoinduced torque and molecular motors in dye-doped nematics
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Time-resolved and polarization-sensitive fluorescence and dichroism in absorbing liquids
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Optical second harmonic generation from LaAlO3/SrTiO3 interfaces with different in-plane anisotropies
No full textOxide growth with semiconductor-like accuracy allows the fabrication of atomically precise thin films and interfaces displaying a wide range of phases and functionalities that are absent in the corresponding oxide bulk materials. Among the other properties it was found that a two-dimensional electronic gas is formed under some circumstances at the LaAlO3/SrTiO3(0 0 1) interface separating two typical insulating perovskite crystals. The origin of this conducting state has been discussed at length, since different doping mechanisms can act in these material systems. Many experimental results point to the so-called polar catastrophe scenario as the principal mechanism driving the formation of the two-dimensional electronic gas. According to this mechanism, the existence of an interfacial polar discontinuity is the key ingredient to drive an electronic reconstruction at the LaAlO3/SrTiO3(0 0 1) interface and the consequent formation of a two-dimensional electron gas. This simple picture has been often questioned by the existence of material systems whose interface are predicted being non-polar according to the simplistic 'ionic' limit but that display an electrical behavior analogous to that of LaAlO3/SrTiO3(0 0 1) interfaces. This is the case of the LaAlO3/SrTiO3(1 1 0), i.e., a LaAlO3/SrTiO3 interface with a different in-plane orientation. It is evident that to solve such kind of controversies a detailed investigation of the polar or non-polar state of these interfaces is needed, although this is not simple for the lack of experimental tools that are specifically sensitive to interfacial polarity. Here we apply Optical Second Harmonic Generation to investigate LaAlO3/SrTiO3 interfaces with different in-plane orientations to bridge this gap. By comparing our results with recent theoretical findings, we will arrive to the conclusion that the real LaAlO3/SrTiO3(1 1 0) interface is strongly polar
Large deuterium isotope effect in the rotational diffusion of anthraquinone dyes in liquid solution
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