Magnetic Field Dependence of the Relaxation Rate of Optically Oriented Nuclei: An Investigation of the Adsorption of Mercury

The magnetic field dependence of the nuclear relaxation rate ${\tau }^{-1\mathrm{}}$ of an optically oriented ${}_{}{}^{199}{}_{}{}^{}\mathrm{Hg}$ vapor confined in a quartz cell is investigated both theoretically and experimentally. A theoretical expression is obtained for ${\tau }^{-1\mathrm{}}$ as a function of the static magnetic field, the average time of flight ${\tau }_f$, the average adsorption time ${\tau }_a$, and other physical parameters characterizing the atom-surface interaction. When the experimental values of ${\tau }^{-1\mathrm{}}$ in the presence of a field ranging between 0 and 1200 G are fitted by this expression, ${\tau }_a$, a good approximation for ${\tau }_f$, and information on the other parameters are easily obtained. The adsorption energy has been evaluated to within 20% using values of ${\tau }_a$ at various temperatures, for the case of an uncoated quartz cell and of a silicone-coated cell. They are 4 and 1.5 kcal/mole, respectively, while ${\tau }_a$ ranges from 5 μsec (at 288 K) to 1.8 μsec (at 328 K) in the former case, from 2.4 μsec (at 281 K) to 1 μsec (at 392 K) in the latter, with a 10% uncertainty.