  We present ultrahigh-resolution measurements of state-to-state inelastic
differential cross sections for NO-Ne and NO-Ar collisions, obtained by
combining the Stark deceleration and velocity map imaging techniques. We show
that for counterpropagating crossed beam geometries, the effect of the velocity
spreads of the reagent beams on the angular resolution of the images is
minimized. Futhermore, the counterpropagating geometry results in images that
are symmetric with respect to the relative velocity vector. This allows for the
use of inverse Abel transformation methods that enhance the resolution further.
State-resolved diffraction oscillations in the differential cross sections are
measured with an angular resolution approaching 0.3$^\circ$. Distinct
structures observed in the cross sections gauge the quality of recent \emph{ab
initio} potential energy surfaces for NO-rare gas atom collisions with
unprecedented precision.
