Wednesday, January 09, 2008

Hiyam's Journal Update

Phys. Rev. B 76, 245209 (2007)
1H NMR electron-nuclear cross relaxation in thin films of hydrogenated amorphous silicon
Tining Su and P. C. Taylor, G. Ganguly and D. E. Carlson, D. C. Bobela, P. Hari

We investigate the spin-lattice relaxation of the dipolar order in 1H NMR in hydrogenated amorphous silicon (a-Si:H). We find that the relaxation is dominated by the cross relaxation between the hydrogen nuclei and the paramagnetic states. The relaxation is inhomogeneous, and can be described as a stretched exponential function. We proposed a possible mechanism for this relaxation. This mechanism applies to a rather broad range of paramagnetic states, including the deep neutral defects (dangling bonds), the light-induced metastable defects, the defects created by doping, and the singly occupied, localized band-tail states populated by light at low temperatures. The cross relaxation is only sensitive to the bulk spin density, and the surface spins have a negligible effect on the relaxation.

Phys. Rev. B 76, 172101 (2007)
1H and 31P nuclear magnetic resonance study of proton-irradiated KH2PO4
Se-Hun Kim,1,2 Kyu Won Lee,1 B. H. Oh,1 Cheol Eui Lee,1 and K. S. Hong3

We have studied the microscopic structure and dynamics in a proton-irradiated KH2PO4 single crystal. Our 1H and 31P nuclear magnetic resonance measurements indicate that proton irradiation gives rise to a decrease in the local dipolar order of the rigid lattice protons and an increase in interstitial protons as well as structural distortion of the PO4 tetrahedra.

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