The cross section of single-electron capture in slow H- + A(3+) --> H + A(2
+)(n) collisions is calculated in the one-electron approximation by using t
he close coupling approach. It is found that the change of the electronic c
onfiguration, that takes place at every avoided crossing of the ionic and c
ovalent energy terms, is a source of nonadiabatic transitions in the system
. This effect leads to a substantial increase of the total cross section an
d produces an effective repopulation of individual covalent states.