From Ultraslow to Extremely Fast Dynamics in Sodium Nitrate: an 17O NMR Study

Abstract

Increasing dynamics in solids featuring nuclei subjected to second-order quadrupolar interactions lead to central-transition spectra that undergo two consecutive line-shaped transitions. Conventional motional narrowing occurs when the molecular exchange rate is on the order of the strength of the dominant interaction. In a second step, the resulting intermediately narrowed spectra change further when the motion becomes faster than the Larmor precession rate, leading to terminally narrowed spectra that can display a residual quadrupolar shift. We derive analytic expressions for this shift and analyze the quadrupolar central-transition spectra in terms of CN symmetrical cone models. Increasing the number of sites to N ≥ 3, the terminally narrowed spectra remain unaltered, while the intermediately narrowed spectra remain unaltered only for N ≥ 5. This finding relates to the different (cubic vs. icosahedral) symmetries that are required to average out the spatial second- and fourth-rank terms in the second-order quadrupolar interaction. Following recent work (Hung et al., Solid State Nucl Magn Reson 84:14–19, 2017), 17O NMR is applied to examine the three-site rotation of the nitrate group in NaNO3. Line shapes are measured and analyzed, and in addition to prior work, satellite-transition and stimulated-echo experiments are carried out. The final-state amplitudes extracted from the latter are reproduced using model calculations. It is shown how two-dimensional exchange spectra relating to N-site cone motions can be decomposed in terms of effective two-site-jump spectra. This latter approach is successfully tested for NaNO3.

Paramagnetic Properties of [AnIV(NO3)6]2− Complexes (An = U, Np, Pu) Probed by NMR Spectroscopy and Quantum Chemical Calculations

“…For the Th IV , Np IV , and Pu IV complexes, the O int peak appears at 427, 442, and 429 ppm, respectively, and probably overlaps the signal of O ext because the O int peak line width is at least 1000 Hz large (≈20 ppm). Nitrate anions may undergo a fast 3-fold jumps at room temperature as observed in the NaNO 3 solid state . Hung et al determined an exchange constant rate of about 10 7 Hz at room temperature by simulating 17 O solid-state NMR spectra .…”

Time Scales of the Quasitetrahedral Motion in KMnO4 Observed by 17O Central-Transition NMR Spectroscopy

“…This is also possible for the quasitetrahedral tensor arrangement sketched in the Supporting Information. Using the procedures outlined in refs and for first-order anisotropies, this yields This quantity varies from 0 to 1/12 for η from 0 to 1, respectively. The result for η = 0 is compatible with previous numerical simulations .…”

“…This is also possible for the quasitetrahedral tensor arrangement sketched in the Supporting Information. Using the procedures outlined in refs and for first-order anisotropies, this yields …”