Cross sections resulting from scattering that proceeds via an intermediate
resonance are shown to be exceptionally controllable using a coherent
superposition of only two intial states. Full quantum computations on
F+HD(v=0;j=0,1) --> H+DF, D+HF, which exhibits a resonance in one of the
reactive channels, support the formal arguments, showing that control is indeed
vast. In this case the ratio of reactive integral cross sections can be altered
by a factor of 62 (compared to a noncoherent factor of only 3.3), while the
ratio of reactive differential cross sections can be altered by a factor of
over 6000 (compared to a noncoherent factor of less than 7). These results
constitute the first prediction of extensive quantum control in a collisional
process.Comment: 9 pages, 1 figur