Relaxation behavior of laser-polarized 129Xe gas:: Size dependency and wall effect of the T1 relaxation time in glass and gelatin bulbs

Size dependency of the relaxation time T-1 was measured for laser-polarized Xe-129 gas encapsulated in different sized cavities made by glass bulbs or gelatin capsules, The use of laser-polarized gas enhances the sensitivity a great deal, making it possible to measure the longer Xe-129 relaxation time in quite a short time. The size dependency is analyzed on the basis of the kinetic theory of gases and a relationship is derived in which the relaxation rate is connected with the square inverse of the diameter of the cavity. Such an analysis provides a novel parameter which denotes the wall effect on the relaxation rate when a gas molecule collides with the surface once in a second. The relaxation time of Xe-129 gas is also dependent on the material which forms the cavity. This dependency is large and the relaxation study using polarized Xe-129 gas is expected to offer important information about the state of the matter of the cavity wall. (C) 2001 Academic Press.