[en] The sorption of dimethyl ether in zeolite H-rho was studied by deuterium NMR of the deuteriated sorbate. The line shapes depend strongly on the temperature and the loading. These changes are not due to dynamic line-broadening effects but rather to changing distributions of sites with different modes of motion. At low loading levels the molecules are rigidly bound and can be seen to undergo 180⁰ flips about the C/sub 2v/ axes. When the number of sorbed molecules exceeds that of the available acid sites (12 per unit cell) most of the molecules appear to be in a physisorbed state