  We exactly solve a Fokker-Planck equation by determining its eigenvalues and
eigenfunctions: we construct nonlinear second-order differential operators
which act as raising and lowering operators, generating ladder spectra for the
odd and even parity states. These are staggered: the odd-even separation
differs from even-odd. The Fokker-Planck equation describes, in the limit of
weak damping, a generalised Ornstein-Uhlenbeck process where the random force
depends upon position as well as time. Our exact solution exhibits anomalous
diffusion at short times and a stationary non-Maxwellian momentum distribution.
