For studying reactions between ions and metal atoms, a temperature variable ring electrode trap (RET) has been combined with an atomic beam source. In , special attention is given to the calibration of the number density of the Ni atoms, injected along the axis of the trap from a metal evaporator. In , an unexpected isotope effect is reported for the reaction O 2 + +Ni->NiO + +O. The isotope 5 8 Ni reacts with a rate coefficient k(670K)=(8+/-2)x10 - 1 0 cm 3 s - 1 , whereas 6 0 Ni reacts two times slower. Formation of Ni 2 + dimers by ternary reactions with He, H 2 , and D 2 as buffer gas is very slow while, in the presence of N 2 , efficient formation of Ni 2 + has been observed via a catalytic cycle utilizing Ni(N 2 ) n + , n=1-3, as intermediate. The rate coefficient for production of Ni 2 + in collisions of NiN 2 + with Ni has been determined to be k(1060K)=(1.7+/-0.7)x10 - 1 0 cm 3 s - 1 .