Effects of Diffusion on Free Precession in Nuclear Magnetic Resonance Experiments Export

@article{citeulike:2617162, abstract = {Nuclear resonance techniques involving free precession are examined; and; in particular; a convenient variation of Hahn's spin-echo method is described. This variation employs a combination of pulses of different intensity or duration ("90-degree" and "180-degree" pulses). Measurements of the transverse relaxation time T 2 in fluids are often severely compromised by molecular diffusion. Hahn's analysis of the effect of diffusion is reformulated and extended; and a new scheme for measuring T 2 is described which; as predicted by the extended theory; largely circumvents the diffusion effect. On the other hand; the free precession technique; applied in a different way; permits a direct measurement of the molecular self-diffusion constant in suitable fluids. A measurement of the self-diffusion constant of water at 25°C is described which yields D =2.5(±0.3)×10 -5 cm 2 /sec; in good agreement with previous determinations. An analysis of the effect of convection on free precession is also given. A null method for measuring the longitudinal relaxation time T 1 ; based on the unequal-pulse technique; is described.}, author = {Carr, H. Y. and Purcell, E. M.}, citeulike-article-id = {2617162}, citeulike-linkout-0 = {http://dx.doi.org/10.1103/PhysRev.94.630}, citeulike-linkout-1 = {http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1954PhRv...94..630C}, citeulike-linkout-2 = {http://link.aps.org/abstract/PR/v94/i3/p630_1}, citeulike-linkout-3 = {http://link.aps.org/pdf/PR/v94/i3/p630_1}, doi = {10.1103/PhysRev.94.630}, journal = {Physical Review Online Archive (Prola)}, keywords = {classic, nmr-diffusion}, month = {May}, number = {3}, pages = {630--638}, posted-at = {2009-11-10 19:34:08}, priority = {2}, publisher = {American Physical Society}, title = {Effects of Diffusion on Free Precession in Nuclear Magnetic Resonance Experiments}, url = {http://dx.doi.org/10.1103/PhysRev.94.630}, volume = {94}, year = {1954} }

TY - JOUR ID - citeulike:2617162 L3 - citeulike-article-id:2617162 N2 - Nuclear resonance techniques involving free precession are examined; and; in particular; a convenient variation of Hahn's spin-echo method is described. This variation employs a combination of pulses of different intensity or duration ("90-degree" and "180-degree" pulses). Measurements of the transverse relaxation time T 2 in fluids are often severely compromised by molecular diffusion. Hahn's analysis of the effect of diffusion is reformulated and extended; and a new scheme for measuring T 2 is described which; as predicted by the extended theory; largely circumvents the diffusion effect. On the other hand; the free precession technique; applied in a different way; permits a direct measurement of the molecular self-diffusion constant in suitable fluids. A measurement of the self-diffusion constant of water at 25°C is described which yields D =2.5(±0.3)×10 -5 cm 2 /sec; in good agreement with previous determinations. An analysis of the effect of convection on free precession is also given. A null method for measuring the longitudinal relaxation time T 1 ; based on the unequal-pulse technique; is described. IS - 3 JF - Physical Review Online Archive (Prola) EP - 638 TI - Effects of Diffusion on Free Precession in Nuclear Magnetic Resonance Experiments PB - American Physical Society VL - 94 SP - 630 KW - classic KW - nmr-diffusion AU - Carr, HY AU - Purcell, EM PY - 1954/May// UR - http://dx.doi.org/10.1103/PhysRev.94.630 ER -