  A separable $x-y$ model is solved for a specialized vector potential (no
magnetic and weak electric fields) penetrating slowly\textbf{,} adiabatically
into and across a rectangular box to which an electron is confined. The
time-dependent Schr\"odinger equation has adiabatic solutions, in which gradual
phase acquisitions occur for {\it parts} of the electronic wave function. For a
closed trajectory of the source, the initial and after-return wave functions
are shown to be simultaneously co-degenerate solutions of the Hamiltonian,
which situation repeats itself for further cyclic motion of the source.
