Revisiting the Van Vleck second moment for characterizing molecular motion in organic solids

Van Vleck’s classic theory of the second moment of lineshapes in 1H nuclear magnetic resonance (NMR) is reworked in a form that allows the effect of rapid molecular motion on second moments to be calculated in a semi-analytical fashion. This is much more efficient than existing approaches and also e...

Full description

Saved in:
Bibliographic Details
Published in:The Journal of chemical physics 2023-06, Vol.158 (24)
Main Authors: Sturniolo, Simone, Wickins, Helen M., Hodgkinson, Paul
Format: Article
Language:English
Subjects:
Chain dynamics
Couplings
Mathematical analysis
Molecular motion
NMR
Nuclear magnetic resonance
Organic solids
Physics
Source code
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Van Vleck’s classic theory of the second moment of lineshapes in 1H nuclear magnetic resonance (NMR) is reworked in a form that allows the effect of rapid molecular motion on second moments to be calculated in a semi-analytical fashion. This is much more efficient than existing approaches and also extends previous analyses of (non-dynamic) dipolar networks in terms of site-specific root-sum-square dipolar couplings. The non-local nature of the second moment means that it can discriminate between overall motions that are difficult to discriminate using alternative approaches, such as measurements of NMR relaxation. The value of reviving second moment studies is illustrated on the plastic solids diamantane and triamantane. In the case of triamantane, straightforward measurements of 1H lineshapes on milligram samples show that the molecules in the higher temperature phase undergo multi-axis jumps, information that is not accessible either to diffraction studies or to alternative NMR approaches. The efficiency of the computational methods means that the second moments can be calculated using a readily extensible and open-source Python code.
ISSN:0021-9606
1089-7690
DOI:10.1063/5.0151022