We have extended our studies of collisional processes in gases at ultracold and cold temperatures in researches that are responsive to experiments. We have calculated the 2Sg+ and 2Su+ potential curves of the molecular ion Yb2+ and we have obtained the cross-sections for charge exchange of its several isotopes of Yb 2 + in the parent gas. We are extending the theory to the case where the ion and the atom are different isotopes and there is a small energy defect. We have extended an investigation of long-range interactions of hydrogen atoms to the n=10 excited Rydberg states (Vrinceanu and Dalgarno 2008). We have explored the mechanisms for the spin depolarization of alkali metal atoms in cold 3 He gas in a joint study with the experimental group.