Charge transfer and elastic scattering probabilities were measured for half
collisions between very slow protons and atomic deuterium. Collision energ
ies down to a few meV, lower by more than an order of magnitude and with be
tter energy resolution than previous measurements, were studied using the d
issociation of the HD+ electronic ground state. The collision energy is det
ermined a posteriori from the measured momentum vector of the dissociating
charged fragments. The experimental results are in good agreement with our
coupled channel calculations.