Direct detection of spin waves in gaseous 3He↑
Résumé
In gaseous spin-polarized 3He at low temperature, spin-diffusion becomes oscillatory and gives rise to spin waves; these waves have a quality factor μM, where M is the (relative) nuclear magnetization and μ a dimensionless coefficient characteristic of the importance of exchange effects in binary collisions. We describe here an NMR technique where these oscillatory modes are directly excited and detected, with the use of two sets of radiofrequency coils (for induction and detection), each connected in opposition in order to create or detect pure magnetization gradients over the sample. The measurements of μ are in good agreement with theory as well as with previous experiments, but only at temperatures above 2 K; below, the measurements are affected by processes which are not fully understood, probably related to the formation of a 3He monolayer on the surface of the coating of solid hydrogen which covers the inner surface of the cell.
Mots clés
gaseous spin polarized sup 3 He
solid H coating
sup 3 He monolayer formation
spin waves
nuclear magnetic resonance
magnetisation
helium
diffusion in gases
electron spin polarisation
exchange interactions electron
spin diffusion
quality factor
nuclear magnetization
exchange effects
binary collisions
NMR technique
oscillatory modes
radiofrequency coils
pure magnetization gradients
Origine | Accord explicite pour ce dépôt |
---|