Quasielastic and inelastic neutron scattering study of methyl group rotation in solid and liquid pentafluoroanisole and pentafluorotoluene

Smuda C, Gemmecker G, Unruh T (2008)

Publication Status: Published

Publication Type: Journal article

Publication year: 2008

Journal

Journal of Chemical Physics AIP Publishing

Publisher: AMER INST PHYSICS

Book Volume: 128

Journal Issue: 19

DOI: 10.1063/1.2894847

Abstract

The rotational motion of the methyl group in pentafluoroanisole (PFA) and in pentafluorotoluene (PFT), respectively, was investigated by quasielastic neutron scattering (QENS). For solid PFA, the rotation can be described by a model for uniaxial rotational jumps between three equidistant sites on a circle. Similar to the molecular structure of alpha-toluene, two nonequivalent methyl groups in the unit cell with two different rotational barriers were found for solid PFT. From the analysis of the quasielastic scattering, the activation energies were determined. The barrier heights could be evaluated from bands in the inelastic part of the spectra. The methyl group dynamics in the liquid state is evaluated for both substances using different scattering functions, which are discussed. An empirical model for the description of the contribution of methyl groups in liquids of small organic molecules to the QENS spectra is presented. It is demonstrated that the process of methyl group rotation in the liquid phase is nearly free of a barrier. (c) 2008 American Institute of Physics.

Authors with CRIS profile

Tobias Unruh Professur für Nanomaterialcharakterisierung (Streumethoden)

Involved external institutions

Technische Universität München (TUM) DE Germany (DE)

How to cite

APA:

Smuda, C., Gemmecker, G., & Unruh, T. (2008). Quasielastic and inelastic neutron scattering study of methyl group rotation in solid and liquid pentafluoroanisole and pentafluorotoluene. Journal of Chemical Physics, 128(19). https://doi.org/10.1063/1.2894847

MLA:

Smuda, Christoph, Gerd Gemmecker, and Tobias Unruh. "Quasielastic and inelastic neutron scattering study of methyl group rotation in solid and liquid pentafluoroanisole and pentafluorotoluene." Journal of Chemical Physics 128.19 (2008).

BibTeX: Download