scholarly journals Broadband Terahertz Spectroscopy of Phonon-Polariton Dispersion in Ferroelectrics

Photonics ◽  
2018 ◽  
Vol 5 (4) ◽  
pp. 55 ◽  
Author(s):  
Seiji Kojima
Keyword(s):  
Electromagnetic Waves ◽  
Terahertz Spectroscopy ◽  
Far Infrared ◽  
Longitudinal Optical ◽  
Vibrational Modes ◽  
Terahertz Time Domain Spectroscopy ◽  
Raman Scattering Spectroscopy ◽  
Longitudinal Optical Mode ◽  
Relationship Of ◽  
The Relationship

Electromagnetic waves at frequencies below the X-ray region strongly couple to the optical vibrational modes in a solid. These coupled excitations have been called phonon polaritons. The relationship of the polariton frequency versus the polariton wavevector shows a remarkable dispersion, especially in the vicinity of the transverse and longitudinal optical mode frequencies. The significant frequency dependence enables valuable applications such as a tunable terahertz radiation source. The polariton dispersion relations of technologically important dielectric and ferroelectric crystals were reviewed in the broad terahertz range using terahertz time-domain spectroscopy, far-infrared spectroscopy, and Raman scattering spectroscopy.

scholarly journals The Status of the Dirbe Instrument on the COBE

1990 ◽  
Vol 123 ◽  
pp. 19-19
Author(s):  
M.G. Hauser ◽  
T. Kelsall ◽  
H. Moseley ◽  
R. Silverberg ◽  
T.L. Murdock ◽  
...  
Keyword(s):  
Far Infrared ◽  
Spin Axis ◽  
Zodiacal Light ◽  
Advantages And Disadvantages ◽  
Bolometric Detectors ◽  
Cosmic Background ◽  
The Status ◽  
Infrared Background ◽  
Relationship Of ◽  
The Relationship

AbstractThe Diffuse Infrared-Background Experiment (DIRBE) on the Cosmic Background Explorer (COBE) satellite is a 10-band absolute photometer covering the wavelengths 1–300 microns using photovoltaic, photoconductive, and bolometric detectors. The input is via a 19-cm, off-axis, highly-baffled Gregorian telescope, with the detectors located at a pupil plane so they share the same field of view (0.7 × 0.7 degrees). The whole assembly is mounted inside a 1.4 K; super-fluid, liquid-He dewar, which is shared with the Far Infrared Absolute Spectrometer (FIRAS) instrument. Each day half of the sky is surveyed, as the line-of-sight of the DIRBE is canted 30 degrees to the COBE spin axis. The whole sky is fully observed in 6 months, as the spin axis precesses at about 1 degree per day. At present each sky pixel has been observed at least once. The basic findings on the general brightness of the sky - Zodiacal light and galaxy - are provided, as well as a synopsis of the advantages and disadvantages associated with a space-borne observatory. The relationship of our experience and findings with respect to possible future missions and their scientific goals is presented.

scholarly journals Spatially Resolving Anharmonic Lattice Dynamics in Molecular Crystals With X-Ray Diffraction and Terahertz Spectroscopy

2019 ◽  
Author(s):  
Martin Hutereau ◽  
Peter Banks ◽  
Ben Slater ◽  
J. Axel Zeitler ◽  
Andrew Bond ◽  
...  
Keyword(s):  
Terahertz Spectroscopy ◽  
Molecular Crystals ◽  
Low Frequency ◽  
Structural Data ◽  
X Ray Diffraction ◽  
Terahertz Time Domain Spectroscopy ◽  
X Ray ◽  
Anharmonic Lattice ◽  
Thermal Displacements ◽  
The Relationship

<div><div><div><div><p>The combination of X-ray diffraction and low-frequency vibrational spectroscopy has proven to be a powerful method for understanding the relationship between molecular and crystalline structures, dynamics, and the properties of materials. In this work, we show how information obtained from terahertz time-domain spectroscopy (THz-TDS) measurements, coupled with first-principles simulations including anharmonic effects, is able to reconcile specific vibrational motions to the experimentally observed large- amplitude thermal displacements in a pair of isomeric molecular crystals. In particular, we show that a single terahertz mode is responsible for the observed structural data, and provide a framework for predicting and interpreting the origins of related phenomena.</p></div></div></div></div>

Determining the Humidity-Dependent Ortho-to-Para Ratio of Water Vapor at Room Temperature Using Terahertz Spectroscopy

2018 ◽  
Vol 72 (7) ◽  
pp. 1040-1046 ◽  
Author(s):  
Xinyang Miao ◽  
Jing Zhu ◽  
Kun Zhao ◽  
Honglei Zhan ◽  
Wenzheng Yue
Keyword(s):  
Water Vapor ◽  
Gas Phase ◽  
Room Temperature ◽  
Terahertz Spectroscopy ◽  
Terahertz Time Domain Spectroscopy ◽  
Preferential Formation ◽  
Physico Chemical ◽  
Spin Isomers ◽  
Chemical Conditions ◽  
The Relationship

The origin of the water spin isomers observed under various physico-chemical conditions is of great interest, including that of H2O molecules in the gas phase. Here, terahertz time-domain spectroscopy (THz-TDS) was used to study the humidity-dependent ortho-to- para (O/P) ratio of water vapor at room temperature. The relative contents of para and ortho molecules were obtained by fitting the absorption lines of water vapor showing the relationship between the spin isomer contents and humidity. Larger O/P ratios with values of ∼3.2 were observed at lower humidity (<20%) due to the stronger attractive forces of para molecules. The concentration of the ortho isomers then began to decrease at higher humidity (>20%) due to the preferential formation of dimers and clusters at increasing concentrations. Thus, the ratio gradually decreased with increasing humidity.

scholarly journals Transport properties of a class of electromagnetic waves

2007 ◽  
Vol 34 (2) ◽  
pp. 161-171
Author(s):  
David Christie
Keyword(s):  
Transport Properties ◽  
Electromagnetic Waves ◽  
Transport Equations ◽  
Space Time ◽  
Wkb Approximation ◽  
Curved Space ◽  
Dependent Transport ◽  
Relationship Of ◽  
The Relationship

We demonstrate that in many cases, known frame-dependent transport equations for a propagating electromagnetic 2-form in an arbitrarily curved space-time can be replaced by a much simpler set of frame-independent equations. The frame-dependent equations can then be more easily recovered from the simpler set presented here if required. The relationship of such transport equations to the WKB approximation is also briefly discussed.

scholarly journals Resolving Anharmonic Lattice Dynamics in Molecular Crystals With X-Ray Diffraction and Terahertz Spectroscopy

2019 ◽  
Author(s):  
Martin Hutereau ◽  
Peter Banks ◽  
Ben Slater ◽  
J. Axel Zeitler ◽  
Andrew Bond ◽  
...  
Keyword(s):  
Terahertz Spectroscopy ◽  
Molecular Crystals ◽  
Low Frequency ◽  
Structural Data ◽  
X Ray Diffraction ◽  
Terahertz Time Domain Spectroscopy ◽  
X Ray ◽  
Anharmonic Lattice ◽  
Thermal Displacements ◽  
The Relationship

<div><div><div><div><p>The combination of X-ray diffraction and low-frequency vibrational spectroscopy has proven to be a powerful method for understanding the relationship between molecular and crystalline structures, dynamics, and the properties of materials. In this work, we show how information obtained from terahertz time-domain spectroscopy (THz-TDS) measurements, coupled with first-principles simulations including anharmonic effects, is able to reconcile specific vibrational motions to the experimentally observed large- amplitude thermal displacements in a pair of isomeric molecular crystals. In particular, we show that a single terahertz mode is responsible for the observed structural data, and provide a framework for predicting and interpreting the origins of related phenomena.</p></div></div></div></div>

Narrow-Line Waveguide Terahertz Time-Domain Spectroscopy of Aspirin and Aspirin Precursors

2008 ◽  
Vol 62 (3) ◽  
pp. 319-326 ◽  
Author(s):  
N. Laman ◽  
S. Sree Harsha ◽  
D. Grischkowsky
Keyword(s):  
Salicylic Acid ◽  
Time Domain ◽  
Low Frequency ◽  
Far Infrared ◽  
Metal Plate ◽  
Thz Radiation ◽  
Vibrational Modes ◽  
Terahertz Time Domain Spectroscopy ◽  
Time Domain Spectroscopy ◽  
Parallel Plate Waveguide

Low frequency vibrational modes of pharmaceutical molecules are dependent on the molecule as a whole and can be used for identification purposes. However, conventional Fourier transform far-infrared spectroscopy (FT-IR) and terahertz time-domain spectroscopy (THz-TDS) often result in broad, overlapping features that are difficult to distinguish. The technique of waveguide THz-TDS has been recently developed, resulting in sharper spectral features. Waveguide THz-TDS consists of forming an ordered polycrystalline film on a metal plate and incorporating that plate in a parallel-plate waveguide, where the film is probed by THz radiation. The planar order of the film on the metal surface strongly reduces the inhomogeneous broadening, while cooling the waveguide to 77 K reduces the homogeneous broadening. This combination results in sharper absorption lines associated with the vibrational modes of the molecule. Here, this technique has been demonstrated with aspirin and its precursors, benzoic acid and salicylic acid, as well as the salicylic acid isomers 3- and 4-hydroxybenzoic acid. Linewidths as narrow as 20 GHz have been observed, rivaling single crystal measurements.

The relationship of the scleractinian corals to the rugose corals

Paleobiology ◽  
1980 ◽  
Vol 6 (02) ◽  
pp. 146-160 ◽  
Author(s):  
William A. Oliver
Keyword(s):  
Critical Points ◽  
Scleractinian Corals ◽  
Convincing Evidence ◽  
Early Triassic ◽  
Rugose Corals ◽  
History Of ◽  
The Subject ◽  
Relationship Of ◽  
The Relationship ◽  
Biologic Factors

The Mesozoic-Cenozoic coral Order Scleractinia has been suggested to have originated or evolved (1) by direct descent from the Paleozoic Order Rugosa or (2) by the development of a skeleton in members of one of the anemone groups that probably have existed throughout Phanerozoic time. In spite of much work on the subject, advocates of the direct descent hypothesis have failed to find convincing evidence of this relationship. Critical points are:(1) Rugosan septal insertion is serial; Scleractinian insertion is cyclic; no intermediate stages have been demonstrated. Apparent intermediates are Scleractinia having bilateral cyclic insertion or teratological Rugosa.(2) There is convincing evidence that the skeletons of many Rugosa were calcitic and none are known to be or to have been aragonitic. In contrast, the skeletons of all living Scleractinia are aragonitic and there is evidence that fossil Scleractinia were aragonitic also. The mineralogic difference is almost certainly due to intrinsic biologic factors.(3) No early Triassic corals of either group are known. This fact is not compelling (by itself) but is important in connection with points 1 and 2, because, given direct descent, both changes took place during this only stage in the history of the two groups in which there are no known corals.

Skeletal elements of crinoid echinoderms: High-resolution structural and microanalytical results

1983 ◽  
Vol 41 ◽  
pp. 194-195
Author(s):  
D. F. Blake ◽  
L. F. Allard ◽  
D. R. Peacor
Keyword(s):  
High Resolution ◽  
Marine Invertebrates ◽  
Sea Urchins ◽  
Structural Features ◽  
Sea Stars ◽  
High Resolution Tem ◽  
Relationship Of ◽  
The Relationship ◽  
Insight Into

Echinodermata is a phylum of marine invertebrates which has been extant since Cambrian time (c.a. 500 m.y. before the present). Modern examples of echinoderms include sea urchins, sea stars, and sea lilies (crinoids). The endoskeletons of echinoderms are composed of plates or ossicles (Fig. 1) which are with few exceptions, porous, single crystals of high-magnesian calcite. Despite their single crystal nature, fracture surfaces do not exhibit the near-perfect {10.4} cleavage characteristic of inorganic calcite. This paradoxical mix of biogenic and inorganic features has prompted much recent work on echinoderm skeletal crystallography. Furthermore, fossil echinoderm hard parts comprise a volumetrically significant portion of some marine limestones sequences. The ultrastructural and microchemical characterization of modern skeletal material should lend insight into: 1). The nature of the biogenic processes involved, for example, the relationship of Mg heterogeneity to morphological and structural features in modern echinoderm material, and 2). The nature of the diagenetic changes undergone by their ancient, fossilized counterparts. In this study, high resolution TEM (HRTEM), high voltage TEM (HVTEM), and STEM microanalysis are used to characterize tha ultrastructural and microchemical composition of skeletal elements of the modern crinoid Neocrinus blakei.

Studies on Leukemogenic and Sarcomagenic Viruses

1970 ◽  
Vol 28 ◽  
pp. 156-157
Author(s):  
Leon Dmochowski
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Morphological Properties ◽  
Mode Of Development ◽  
Relationship Of ◽  
The Relationship

Electron microscopy has proved to be an invaluable discipline in studies on the relationship of viruses to the origin of leukemia, sarcoma, and other types of tumors in animals and man. The successful cell-free transmission of leukemia and sarcoma in mice, rats, hamsters, and cats, interpreted as due to a virus or viruses, was proved to be due to a virus on the basis of electron microscope studies. These studies demonstrated that all the types of neoplasia in animals of the species examined are produced by a virus of certain characteristic morphological properties similar, if not identical, in the mode of development in all types of neoplasia in animals, as shown in Fig. 1.

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