NH3D+ dominated proton spin-lattice relaxation in partly deuterated ammonium compounds

Ylinen, E.E.; Filipek, Pauline A.; Punkkinen, M.; Lalowicz, Z. T.

doi:10.1016/j.physb.2004.12.012

Cited by 7 publications

(2 citation statements)

References 22 publications

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“…11,12 Partial deuteration was observed to play a dominant role in the spin-lattice relaxation of both the deuterons and protons in ammonium hexachlorotellurate. 13,14 Deuteron NMR studies provide evidence for diverse mobility in the ordered phase. Ammonium ions inside ordered domains are immobile in ͑ND 4 ͒ 2 PtCl 4 at low temperatures.…”

Section: Introductionmentioning

confidence: 99%

Deuteron NMR relaxation, spectra, and evidence for the order-disorder phase transition in (ND4)2PtCl6

Birczyński

Ylinen

Punkkinen

et al. 2008

The Journal of Chemical Physics

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Deuteron NMR relaxation and spectra were studied at the resonance frequency of 46 MHz in polycrystalline (ND(4))(2)PtCl(6) between 300-5 K. The relaxation rate maximum near 50 K is about 53% smaller than the calculated maximum related to 120 degrees rotations about the threefold symmetry axes of the ammonium ion. The difference is explained by assuming for a N-D vector a total of 24 equilibrium directions, which in groups of six deviate from the nearest Pt-N vector by a certain angle Theta. So-called limited jumps between the directions of each group take place much more frequently than the large-angle rotations, thus rendering a fraction of the deuteron quadrupole coupling ineffective in relaxation. A motional model is presented, which takes into account both these motions simultaneously. A comparison with experimental data leads to Theta=26.0 degrees , in reasonable agreement with earlier neutron diffraction data. A sharp decrease found in the relaxation rate at the order-disorder phase transition temperature of 27.2 K is related to the fact that one of the six equilibrium directions becomes preferred. This leads to a formation of ordered domains, in which the active motion driving the relaxation is 120 degrees rotations. Two components in the spectra found below 55 K are related to domains (broad) and transition regions between domains (narrow). Reasons for the nonexponentiality observed below 20 K are discussed, the most likely explanation being that limited jumps dominate within transition regions and make the corresponding deuterons relax faster than those in domains.

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Section: Introductionmentioning

confidence: 99%

Deuteron NMR relaxation, spectra, and evidence for the order-disorder phase transition in (ND4)2PtCl6

Birczyński

Ylinen

Punkkinen

et al. 2008

The Journal of Chemical Physics

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“…Detailed explanations for the shortening were slow to appear. One reason was suggested to be the additional tunnelling splittings related to NH 3 D þ ions [2]. The dominant factor, however, seems to be the increased motional rate of NH 3 D þ and other partly deuterated ammonium ions, which increase also the deuteron relaxation rate by several orders of magnitude in partly deuterated compounds relative to 100% deuterated samples [3,4].…”

Section: Introductionmentioning

confidence: 99%