  We study the scattering of two-level atoms at narrow laser fields, modeled by
a $\delta$-shape intensity profile. The unique properties of these potentials
allow us to give simple analytic solutions for one or two field zones. Several
applications are studied: a single $\delta$-laser may serve as a detector model
for atom detection and arrival-time measurements, either by means of
fluorescence or variations in occupation probabilities. We show that, in
principle, this ideal detector can measure the particle density, the quantum
mechanical flux, arrival time distributions or local kinetic energy densities.
Moreover, two spatially separated $\delta$-lasers are used to investigate
quantized-motion effects on Ramsey interferometry.
