01661nas a2200229 4500008004100000245005800041210005800099300001600157490000800173520102600181100001401207700001901221700001401240700001301254700001901267700002201286700001501308700001801323700002101341700002001362856004901382 2021 eng d00aPhonon Kinetics of Fructose at the Melting Transition0 aPhonon Kinetics of Fructose at the Melting Transition a12269-122760 v1253 a
Terahertz time domain spectroscopy (THz TDS) is used to measure the melting kinetics of fructose molecular crystals. Combining single-crystal anisotropy measurements with density functional calculations, we assign the phonon frequencies and interrogate how specific phonons behave with melting. While nearly all the low-frequency phonons continuously red-shift with heating and melting, the lowest-energy phonon polarized along the c-axis blue-shifts at the melting temperature, suggesting an initial structural change immediately before melting. We find that the kinetics follow a 3D growth model with large activation energies, consistent with previous differential scanning calorimetry (DSC) measurements. The large activation energies indicate that multiple H-bonds must break collectively for the transition. The results suggest the generality of the kinetics for molecular crystals and that THz TDS with picosecond resolution could be used to measure ultrafast kinetics.
1 aDavie, A.1 aVandrevala, F.1 aDampf, S.1 aDeng, Y.1 aGeorge, D., K.1 aSylvester, E., D.1 aKorter, T.1 aEinarsson, E.1 aBenedict, J., B.1 aMarkelz, A., G. uhttps://markelz.physics.buffalo.edu/node/52001834nas a2200385 4500008004100000020001400041245007100055210006900126260002400195300001000219520062400229653001500853653003100868653002700899653003400926653003400960653004300994653001501037653002301052653003001075653001501105653001301120653004501133653002701178653001701205653002201222653002701244653002701271653004101298653001501339100001301354700001601367700001601383856004901399 2019 eng d a2162-203500aAngular Distortion Removal of THz Anisotropic Dichroism Microscope0 aAngular Distortion Removal of THz Anisotropic Dichroism Microsco aParis, Francec2019 a1 - 23 a
We have developed a stationary sample THz anisotropic dichroism microscope as a powerful tool for material characterization. The key innovation is the use of an iso-response curve defined by the terahertz and detection light polarizations. Here we show that following a continuous iso-response curve introduces angular distortion in the spectrum, and this distortion can be eliminated by using a discontinuous iso-response angle pairs avoiding large gradient regions. Employing this additional constraint on the relative polarizations provides a convenient technique for rapid anisotropic terahertz spectroscopy.
10aabsorption10aangular distortion removal10aBiomedical measurement10acontinuous iso-response curve10adetection light polarizations10adiscontinuous iso-response angle pairs10aDistortion10alight polarisation10amaterial characterization10aMicroscopy10aproteins10arapid anisotropic terahertz spectroscopy10arelative polarizations10aspectroscopy10astationary sample10aterahertz spectroscopy10aterahertz wave spectra10aTHz anisotropic dichroism microscope10avibrations1 aDeng, Y.1 aNiessen, K.1 aMarkelz, A. uhttps://ieeexplore.ieee.org/document/8873793