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.

%B J. Phys. Chem. C %V 125 %P 12269-12276 %G eng %N 22 %& 12269 %R 10.1021/acs.jpcc.1c00610 %0 Conference Proceedings %B Nonlinear Optics: Materials, Fundamentals, and Applications %D 2000 %T High field pulsed terahertz measurements of nonlinear conductivity %A A. G. Markelz %K 0.5 THz %K 2D electron gases %K Conductivity measurement %K electrical conductivity measurement %K Electron emission %K FEL measurements %K Finite impulse response filter %K high field pulsed terahertz measurements %K high field pulsed terahertz spectroscopy %K high-speed optical techniques %K inplane nonlinear conductivity response %K LO phonon bottleneck weakening %K nonlinear conductivity %K nonlinear optics %K phonons %K Power measurement %K Pulse measurements %K Resonance %K semiconductor quantum wells %K spectroscopy %K Submillimeter wave measurements %K submillimetre wave spectroscopy %K two dimensional electron gases %K two-dimensional electron gas %X

High field pulsed terahertz spectroscopy is used to measure the inplane nonlinear conductivity response of two dimensional electron gases. Results are compared to FEL measurements suggesting LO phonon bottleneck weakening at 0.5 THz.

%B Nonlinear Optics: Materials, Fundamentals, and Applications %7 Postconference %C Kaua'i-Lihue, HI, USA %V 46 %P 105 - 106 %8 2000 %G eng %U https://ieeexplore.ieee.org/document/883591/authors#authors %! Nonlinear Optics: Materials, Fundamentals, and Applications. Technical Digest. Postconference Edition. TOPS Vol.46 (IEEE Cat. No.00CH37174) %R 10.1109/NLO.2000.883591