  Quantum theory of interference phenomena does not take the diameter of the
particle into account, since particles were much smaller than the width of the
slits in early observations. In recent experiments with large molecules, the
diameter of the particle has approached the width of the slits. Therefore,
analytical description of these cases should include a finite particle size.
The generic quantum interference setup is an asymmetric double slit
interferometer. We evaluate the wave function of the particle transverse motion
using two forms of the solution of Schrodinger's equation in an asymmetric
interferometer: the Fresnel-Kirchhoff form and the form derived from the
transverse wave function in the momentum representation. The transverse
momentum distribution is independent of the distance from the slits, while the
space distribution strongly depends on this distance. Based on the transverse
momentum distribution we determined the space distribution of particles behind
the slits. We will present two cases: a) when the diameter of the particle may
be neglected with respect to the width of both slits, and b) when the diameter
of the particle is larger than the width of the smaller slit.
