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@ARTICLE{Berns:16354,
      author       = {Berns, A.E. and Conte, P.},
      title        = {{E}ffect of ramp size and sample spinning speed on {CPMAS}
                      13{C} {NMR} spectra of soil organic matter},
      journal      = {Organic geochemistry},
      volume       = {42},
      issn         = {0146-6380},
      address      = {Amsterdam [u.a.]},
      publisher    = {Elsevier Science},
      reportid     = {PreJuSER-16354},
      pages        = {926 - 935},
      year         = {2011},
      note         = {The authors thank Forschungszentrum Julich GmbH (Germany)
                      for having financed PC as visiting scientist at the NMR
                      center of the IBG-3: Agrosphere, Institute of Bio- and
                      Geosciences.},
      abstract     = {Cross polarization (CP) magic angle spinning (MAS) C-13 NMR
                      spectroscopy is a solid state NMR technique widely applied
                      to study the chemical composition of natural organic matter.
                      In high magnetic fields (>7 T), fast sample spinning is
                      required in order to reduce the influence of spinning
                      sidebands underlying other chemical shift regions. As the
                      spinning speed increases, the Hartmann-Hahn matching
                      profiles break down into a series of narrow matching bands.
                      In order to account for this instability variable amplitude
                      cross polarization techniques (e.g. VACP, ramp-CP) have been
                      developed. In the present study, we experimentally verified
                      the stability of the Hartmann-Hahn condition under two MAS
                      speeds for different samples with known structure and two
                      different humic acids. For a complete restoration of flat
                      matching profiles, large ramp sizes were needed. The
                      matching profiles of the humic acids showed that both
                      samples needed different ramp sizes to restore flat
                      profiles. A set up based on the matching profiles of the
                      commonly used glycine would have led to an insufficient ramp
                      size for one of the humic acids. For the characterization of
                      natural organic matter, we hence recommend to roughly set
                      the matching conditions with a standard and subsequently
                      optimize the matching conditions on a more complex,
                      preferably representative, sample such as a humic acid. We
                      would suggest to either run an array of different ramp sizes
                      until maximum signal intensity is reached for all chemical
                      shift regions or, in the case of unavailable measurement
                      time, to use a ramp size twice the spinning speed. (C) 2011
                      Elsevier Ltd. All rights reserved.},
      keywords     = {J (WoSType)},
      cin          = {IBG-3},
      ddc          = {540},
      cid          = {I:(DE-Juel1)IBG-3-20101118},
      pnm          = {Terrestrische Umwelt},
      pid          = {G:(DE-Juel1)FUEK407},
      shelfmark    = {Geochemistry $\&$ Geophysics},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000295215300006},
      doi          = {10.1016/j.orggeochem.2011.03.022},
      url          = {https://juser.fz-juelich.de/record/16354},
}