  The time-dependent, geometric method for high-energy limits and inverse
scattering is applied to nonrelativistic quantum particles in external
electromagnetic fields. Both the Schr"odinger- and the Pauli equations in R^2
and R^3 are considered. The electrostatic potential A_0 shall be short-range,
and the magnetic field B shall decay faster than |x|^{-3/2} . A natural class
of corresponding vector potentials A of medium range is introduced, and the
decay and regularity properties of various gauges are discussed, including the
transversal gauge, the Coulomb gauge, and the Griesinger vector potentials. By
a suitable combination of these gauges, B need not be differentiable. The
scattering operator S is not invariant under the corresponding gauge
transformations, but experiences an explicit transformation. Both B and A_0 are
reconstructed from an X-ray transform, which is obtained from the high-energy
limit of S . Here previous results by Arians and Nicoleau are generalized to
the medium-range situation. In a sequel paper, medium-range vector potentials
are applied to relativistic scattering.
