Wide-Angle Polarization Analysis on the Multi-Axis Crystal Spectrometer for the Study of Collective and Single Particle Dynamics of Methanol at its Prepeak

Published

July 1, 2019

Author(s)

Wangchun Chen, Shannon M. Watson, Yiming Qiu, Jose Rodriguez Rivera, Antonio Faraone

Abstract

Neutron polarization analysis capability with a large scattering angle and momentum transfer coverage has not been widely implemented for the separation of coherent and incoherent quasi-elastic neutron scattering (QENS) spectra. A feasibility test for soft condensed matter applications was performed on the Multi-Axis Crystal Spectrometer (MACS) at the NIST Center for Neutron Research (NCNR). This capability benefitted from the high flux wide angle polarization analysis capability recently developed on MACS for hard condensed matter investigations. The experimental procedure is thoroughly described on how to take data and perform polarization efficiency correction before further data analysis is done. This capability was employed to unambiguously separate the coherent and incoherent signal from the QENS spectra for the investigation of both the collective and the single particle dynamics in partially deuterated (CH₃OD, D 99.5 % purity) methanol. By studying a Q range encompassing the prepeak position, it was possible to directly measure the dynamics of the h-bonding associates which originate the prepeak signal, without contamination from the incoherent scattering, in spite of the relative weakness of the coherent scattering.

Citation

Physica B-Condensed Matter

Volume

564

Pub Type

Journals

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Citation

Chen, W. , Watson, S. , Qiu, Y. , Rodriguez Rivera, J. and Faraone, A. (2019), Wide-Angle Polarization Analysis on the Multi-Axis Crystal Spectrometer for the Study of Collective and Single Particle Dynamics of Methanol at its Prepeak, Physica B-Condensed Matter, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=926915 (Accessed October 13, 2025)