Second moment of multiple-quantum NMR and a time-dependent growth of the number of multispin correlations in solids
- Russian Academy of Sciences, Kirenskii Institute of Physics, Siberian Division (Russian Federation), E-mail: rsa@iph.krasn.ru
- Russian Academy of Sciences, Semenov Institute of Chemical Physics (Russian Federation), E-mail: andylun@orc.ru
The time evolution of multispin correlations (the growth of the number of correlated spins as a function of time) can be observed directly using the multiple-quantum nuclear magnetic resonance spectroscopy of solids. A quantity related to this number, namely, the second moment <n{sup 2}(t)> of the intensity distribution of coherences of different orders in the multiple-quantum spectrum can be calculated using the theory proposed in this work. An approach to the calculation of the four-spin time correlation function through which this moment is expressed is developed. The main sequences of contributions in the expansion of this function into a time power series are summed using the approximation of a large number of neighbors both for systems with a secular dipole-dipole interaction and for systems with a nonsecular effective interaction. An exponential dependence of <n{sup 2}(t)> is obtained. The value of <n{sup 2}(t)> is additionally calculated using an expansion in terms of orthogonal operators for three model examples corresponding to different limiting realizations of spin systems. It is shown that the results of the microscopic theory at least qualitatively agree with both the results obtained for model examples and experimental results obtained recently for adamantane.
- OSTI ID:
- 21067586
- Journal Information:
- Journal of Experimental and Theoretical Physics, Vol. 103, Issue 6; Other Information: DOI: 10.1134/S1063776106120089; Copyright (c) 2006 Nauka/Interperiodica; Article Copyright (c) 2006 Pleiades Publishing, Inc; Country of input: International Atomic Energy Agency (IAEA); ISSN 1063-7761
- Country of Publication:
- United States
- Language:
- English
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