MQ NMR dynamics in dipolar ordered state at negative temperature

• Published in: Solid state nuclear magnetic resonance Vol. 61-62; pp. 49 - 53
• Main Authors: Furman, G.B., Goren, S.D., Meerovich, V.M., Sokolovsky, V.L.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Inc 01-07-2014
• Subjects: Coherence; Dipolar ordered state; Dynamic tests; Dynamical systems; Dynamics; Energy (nuclear); Multiple quantum NMR spin dynamics; Negative temperature; Nuclear magnetic resonance; Nuclear spin; Temperature; Dipolar ordered state; Negative temperature; Multiple quantum NMR spin dynamics
• ISSN: 0926-2040; 1527-3326
• DOI: 10.1016/j.ssnmr.2014.05.004

We investigate theoretically the Multiple Quantum (MQ) NMR dynamics at negative absolute temperatures in systems of nuclear spins 1/2 coupled by the dipole–dipole interactions and with the initial conditions determined by the dipolar ordered state. Two different methods of MQ NMR are used. One of them is based on the measurement of the dipolar energy. The other method uses an additional resonance (π/4)y-pulse after the preparation period of the standard MQ NMR experiment. It is shown that at negative temperatures many-spin clusters and spin correlations are created faster, and the intensities of MQ coherences are higher than in the usual MQ NMR experiments. So, the eighth-order MQ coherence in 10-spin system of the cyclopentane molecule appears to be 1.5 times faster and its intensity is four orders higher than at positive temperatures. The proposed MQ NMR methods at negative absolute temperatures can be used for the investigation of many-spin dynamics of nuclear spins in solids.
We investigate theoretically the Multiple Quantum (MQ) NMR dynamics at negative absolute temperatures in systems of nuclear spins 1/2 coupled by the dipole-dipole interactions and with the initial conditions determined by the dipolar ordered state. Two different methods of MQ NMR are used. One of them is based on the measurement of the dipolar energy. The other method uses an additional resonance ϕy-pulse after the preparation period of the standard MQ NMR experiment. [Display omitted]