  A method is presented to calculate the spin relaxation times T1, T2 due to a
non-uniform magnetic field, and the linear-in-electric-field precession
frequency shift {\delta}{\omega}E when an electric field is present, in the
diffusion approximation for spins confined to a rectangular cell. It is found
that the rectangular cell geometry admits of a general result for T1, T2, and
{\delta}{\omega}E in terms of the spatial cosine-transform components of the
magnetic field.
