Three-particle breakup near threshold when the Wannier exponent diverges

Wannier theory predicts an infinite threshold exponent for the breakup of three charged particles if two of the particles have equal charges and the ratio of the charge of one of these to the charge of the third particle has the value (-4). We show that the Wannier picture of ridge propagation remains valid and that the threshold law changes to the form σ∝E^-1/6exp(-κ/E^1/6). The classical and quantum results differ, which is in contrast to the generic Wannier case. We show that the classical limit of the threshold law explains the threshold behavior obtained numerically by classical trajectory calculations.