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111.
The recent introduction of NMR spectrometers with multiple receivers permits spectra from several different nuclear species to be recorded in parallel, and several standard pulse sequences to be combined into a single entity. It is shown how these improvements in the flow and quality of spectral information can be significantly augmented by compressive sensing techniques--controlled aliasing, Hadamard spectroscopy, single-point evaluation of evolution space (SPEED), random sampling, projection-reconstruction, and hyperdimensional NMR. Future developments of these techniques are confidently expected to mitigate one of the most serious limitations in multidimensional NMR--the excessive duration of the measurements. 相似文献
112.
Ray L. Frost Silmarilly Bahfenne Jií ejka Jií Sejkora Sara J. Palmer Radek koda 《Journal of Raman spectroscopy : JRS》2010,41(6):690-693
Raman spectroscopy has been used to study the arsenate minerals haidingerite Ca(AsO3OH)·H2O and brassite Mg(AsO3OH)·4H2O. Intense Raman bands in the haidingerite spectrum observed at 745 and 855 cm−1 are assigned to the (AsO3OH)2−ν3 antisymmetric stretching and ν1 symmetric stretching vibrational modes. For brassite, two similarly assigned intense bands are found at 809 and 862 cm−1. The observation of multiple Raman bands in the (AsO3OH)2− stretching and bending regions suggests that the arsenate tetrahedrons in the crystal structures of both minerals studied are strongly distorted. Broad Raman bands observed at 2842 cm−1 for haidingerite and 3035 cm−1 for brassite indicate strong hydrogen bonding of water molecules in the structure of these minerals. OH···O hydrogen‐bond lengths were calculated from the Raman spectra based on empirical relations. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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115.
The development of an all-solid-state cw laser system for optical absorption measurements of the OH radical in the UV spectral range is described. The tunable output of a 1064-nm external-cavity diode laser is amplified by use of a Nd:doped, double-clad fiber amplifier. The amplified near-IR radiation is frequency doubled by a periodically poled lithium niobate crystal and then quadrupled in a beta-barium borate crystal. The design and operation of the system and measurements of OH absorption in the (2, 0) band of the A(2)?(+)- X(2)? electronic transition are discussed. 相似文献
116.
Sungjin Wi Eljon Elezi Amy C. Liu Vishva Ray Kai Sun Xiaogan Liang 《Applied Physics A: Materials Science & Processing》2013,111(3):755-766
We present a growth process mediated by nanoimprinted nanostructures specifically for producing bismuth selenide (Bi2Se3) topological insulator nanoribbons with a high yield. In this process, topological insulator nanostructures are grown on nanoimprinted gratings by using a nanoparticle-catalyzed vapor–liquid–solid mechanism. In comparison with the growth processes performed on flat and randomly rough substrates, such a nanograting-mediated growth method produces topological insulator nanoribbons with a higher yield (~15?000 nanoribbons/mm2), a narrower average ribbon width (w avg<60 nm), and a higher uniformity in ribbon width (σ<30 nm); effectively suppresses the formation of other unwanted morphologies; and also results in the axial growth of nanoribbons along specific in-plane directions relative to pre-structured gratings. Such technical merits of nanograting-mediated growth are attributed to the preferential nucleation of Bi2Se3 crystal seeds and the concomitant pinning of catalytic nanoparticles at ordered grating edges. Finally, Aharonov–Bohm interference oscillations in the magnetoresistance were observed and demonstrated the coherent transport of electrons through topological surface states of Bi2Se3 nanoribbons. This growth process in combination with large-area nanoimprint lithography could serve as an important foundation for nanomanufacturing topological insulator nanoribbons with controllable feature size, large-area uniformity, and ordering, suitable for applications in future low-dissipation nanoelectronics. 相似文献
117.
Alexopoulos T Arenton M Barbosa RF Barker AR Bellantoni L Bellavance A Blucher E Bock GJ Cheu E Childress S Coleman R Corcoran MD Cox B Erwin AR Ford R Glazov A Golossanov A Graham J Hamm J Hanagaki K Hsiung YB Huang H Jejer V Jensen DA Kessler R Kobrak HG Kotera K LaDue J Ledovskoy A McBride PL Monnier E Nelson KS Nguyen H Niclasen R Prasad V Qi XR Ramberg EJ Ray RE Ronquest M Santos E Shanahan P Shields J Slater W Smith D Solomey N Swallow EC Toale PA Tschirhart R Wah YW Wang J White HB 《Physical review letters》2004,93(18):181802
We present a determination of the Cabibbo-Kobayashi-Maskawa parameter |V(us)| based on new measurements of the six largest K(L) branching fractions and semileptonic form factors by the KTeV (E832) experiment at Fermilab. We find |V(us)|=0.2252+/-0.0008(KTeV)+/-0.0021(ext), where the errors are from KTeV measurements and from external sources. We also use the measured branching fractions to determine the CP violation parameter |eta(+-)|=(2.228+/-0.005(KTeV)+/-0.009(ext))x10(-3). 相似文献
118.
We have used vibrational spectroscopy to study the formula and molecular structure of the mineral penkvilksite Na 2TiSi 4O 11·2H 2O. Penkvilksite is a mineral which may be used in the uptake of radioactive elements. Both Raman and infrared spectroscopies identify a band at ~3638 cm?1 attributed to an OH-stretching vibration of hydroxyl units. The inference is that OH units are involved in the structure of penkvilksite. The formula may be well written as Na 2TiSi 4O 10(OH)2·H 2O. The mineral is characterised by a very intense Raman band at 1085 cm?1 and a broad infrared band at 1080 cm?1 assigned to SiO-stretching vibrations. Raman bands at 620, 667 and 711 cm?1 are attributed to SiO and TiO chain bonds. Water-stretching vibrations are observed as Raman bands at 3197, 3265, 3425 and 3565 cm?1. Vibrational spectroscopy enables aspects of the molecular structure of the mineral penkvilksite to be ascertained. Penkvilksite is a mineral which can incorporate actinides and lanthanides from radioactive waste. 相似文献
119.
Jerry Ray Dias 《Molecular physics》2020,118(12)
Cycloparaphenylene ([r]CPP) and cyclacene ([r]CA) series are models for short carbon nanotubes. It is shown that armchair edges in model cycloparaphenylenes possess greater aromaticity and cyclic conjugation than do zigzag edges in model cyclacenes. According to Aihara’s bond resonance energy (BRE) and Bosanac and Gutman energy effect (ef) measurements, cycloparaphenylenes are twice as aromatic as cyclacenes. The general solution of all eigenvalues of all members of the cycloparaphenylene series is given. The origin of the recurrence of some eigenvalues are determined. 相似文献
120.
A method for the direct gravimetric determination of osmium with 1:2:3-benzotriazole in acetic acid-sodium acetate buffer is presented. The method is accurate and reproducible, and the conditions used in the determination are not critical. The precipitate is a stoichiometric compound which is stable from room temperature up to 200°. It appears that 1:2:3-benzotriazole is probably the first organic reagent to be used successfully in the direct gravimetric determination of osmium. 相似文献