  Stark deceleration allows for precise control over the velocity of a pulsed
molecular beam and, by the nature of its limited phase-space acceptance,
reduces the energy width of the decelerated packet. We describe an alternate
method of operating a Stark decelerator that further reduces the energy spread
over the standard method of operation. In this alternate mode of operation, we
aggressively decelerate the molecular packet using a high phase angle. This
technique brings the molecular packet to the desired velocity before it reaches
the end of the decelerator; the remaining stages are then used to
longitudinally and transversely guide the packet to the detection/interaction
region. The result of the initial aggressive slowing is a reduction in the
phase-space acceptance of the decelerator and thus a narrowing of the velocity
spread of the molecular packet. In addition to the narrower energy spread, this
method also results in a velocity spread that is nearly independent of the
final velocity. Using the alternate deceleration technique, the energy
resolution of molecular collision measurements can be improved considerably.
