  As a submanifold is embedded into higher dimensional flat space, quantum
mechanics gives various embedding quantities, e.g., the geometric momentum and
geometric potential, etc. For a particle moving on a two-dimensional sphere or
a free rotation of a spherical top, the projections of the geometric momentum p
and the angular momentum L onto a certain Cartesian axis form a complete set of
commuting observables as [p_{i},L_{i}]=0 (i=1,2,3). We have therefore a
(p_{i},L_{i}) representation for the states on the two-dimensional spherical
surface. The geometric momentum distribution of the ground states for a freely
rotating rigid rotor seems within the resolution power of present momentum
spectrometer and can be measured to probe the embedding effect.
