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Spin-symmetry conversion in methyl rotors induced by tunnel resonance at low temperature

Zhang, Bo; Sun, Cheng; Alsanoosi, Ali M.; Aibout, Abdellah; Horsewill, Anthony J.

Authors

Bo Zhang ppxbz@nottingham.ac.uk

Cheng Sun

Ali M. Alsanoosi

Abdellah Aibout

Anthony J. Horsewill a.horsewill@nottingham.ac.uk



Abstract

Field-cycling NMR in the solid state at low temperature (4.2 K) has been employed to measure the tunneling spectra of methyl (CH3) rotors in phenylacetone and toluene. The phenomenon of tunnel resonance reveals anomalies in 1H magnetization from which the following tunnel frequencies have been determined: phenylacetone, vt = 6.58+-0.08 MHz ; toluene, vt = 6.45+-0.06 GHz and vt = 7.07+-0.06 GHz. The tunnel frequencies in the two samples differ by three orders of magnitude, meaning different experimental approaches are required. In phenylacetone the magnetization anomalies are observed when the tunnel frequency matches one or two times the 1H Larmor frequency. In toluene, doping with free radicals enables magnetization anomalies to be observed when the tunnel frequency is equal to the electron spin Larmor frequency. Cross-polarization processes between the tunneling and Zeeman systems are proposed and form the basis of a thermodynamic model to simulate the tunnel resonance spectra. These invoke space-spin interactions to drive the changes in nuclear spin-symmetry. The tunnel resonance lineshapes are explained, showing good quantitative agreement between experiment and simulations.

Journal Article Type Article
Publication Date Feb 28, 2014
Journal Journal of Chemical Physics
Print ISSN 0021-9606
Electronic ISSN 0021-9606
Publisher AIP Publishing
Peer Reviewed Peer Reviewed
Volume 140
Issue 8
APA6 Citation Zhang, B., Sun, C., Alsanoosi, A. M., Aibout, A., & Horsewill, A. J. (2014). Spin-symmetry conversion in methyl rotors induced by tunnel resonance at low temperature. Journal of Chemical Physics, 140(8), doi:10.1063/1.4865835
DOI https://doi.org/10.1063/1.4865835
Publisher URL http://scitation.aip.org/content/aip/journal/jcp/140/8/10.1063/1.4865835
Copyright Statement Copyright information regarding this work can be found at the following address: http://eprints.nottingh.../end_user_agreement.pdf
Additional Information © 2014 AIP Publishing LLC

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Copyright Statement
Copyright information regarding this work can be found at the following address: http://eprints.nottingham.ac.uk/end_user_agreement.pdf





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