Magic-angle-spinning 15N NMR of ammonium sulfate
1987; Elsevier BV; Volume: 139; Issue: 3-4 Linguagem: Inglês
10.1016/0009-2614(87)80565-1
ISSN1873-4448
AutoresMarco L.H. Gruwel, Michael S. McKinnon, Roderick E. Wasylishen,
Tópico(s)Electron Spin Resonance Studies
ResumoMagic-angle 15N NMR measurements indicate that the nitrogen chemical shift difference for the two inequivalent ammonium ion sites of (NH4)2SO4 is only 0.30 ppm in the room-temperature phase at 290 K. The implication is that the immediate environment of the two ions is similar; this is supported by T1 (15N) measurements of the two chemically shifted resonances. At temperatures immediately below the known phase transition (T = 223 K) the chemical shift difference between the two sites is 1.2 ppm and the 15N T1 values differ by almost an order of magnitude, implying substantially different environments for the two distinct ammonium ions in the ferroelectric phase.
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