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Title:EXPLORING THE SOLID STATE PHASE TRANSITION IN DL-NORVALINE WITH TERAHERTZ SPECTROSCOPY
Author(s):Schmuttenmaer, Charles A.
Contributor(s):Williams, Michael R. C.; Regan, Kevin P.; Nemes, Coleen T.; Neu, Jens
Subject(s):Mini-symposium: Far-Infrared Spectroscopy
Abstract:DL-Norvaline is a molecular crystal at room temperature and it undergoes a phase transition when cooled below 190 \textit{K}. This phase transition is believed to be Martensitic. We investigate this phase transition by measuring its terahertz (THz) spectrum over a range of temperatures. Temperature-dependent THz time-domain spectroscopy (THz-TDS) measurements reveal that the transition temperature ($\textit{T}_{\beta \rightarrow \alpha}$) is 190 \textit{K}. The influence of nucleation seeds was analyzed by determining the $\textit{T}_{\beta \rightarrow \alpha}$ of molecular crystals with varying grain size. Grains of 5 $\mu$m or less result in a lower transition temperature ($\textit{T}_{\beta \rightarrow \alpha}$ = 180 \textit{K}) compared to larger grains of 125–250 $\mu$m ($\textit{T}_{\beta \rightarrow \alpha}$ = 190 \textit{K}). Additionally, we gain insight into the physical process of the phase transition \textit{via} temperature-dependent THz-TDS spectra of doped and mixed molecular crystals. The addition of molecular dopants, which differ from DL-norvaline only at the end of the side chain which resides in the hydrophobic layers of the crystal, decreases $\textit{T}_{\beta \rightarrow \alpha}$. This is consistent with a solid-solid phase transition in which the unit cell shifts along this hydrophobic layer, and it leads us to believe that the phase transition in DL-norvaline is Martensitic in nature.
Issue Date:06/20/18
Publisher:International Symposium on Molecular Spectroscopy
Citation Info:APS
Genre:Conference Paper / Presentation
Type:Text
Language:English
URI:http://hdl.handle.net/2142/100844
DOI:10.15278/isms.2018.WI05
Other Identifier(s):WI05
Date Available in IDEALS:2018-08-17
2018-12-12


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