Two particular collision processes involving electron transfer are investigated that may have impact on the analyses of ion flux data obtained in the CRRES G-1 and G-11b, upper atmospheric chemical release experiments. Ion pair production (&sgr;IP) and charge exchange ionization (&sgr;CE) cross sections are calculated as a function of collision energy for reactions between Ba/Sr atoms and O atoms and O+ ions, respectively, using two-state approximation theories. The cross sections for each process are calculated for both the ground and metastable states of the metal atoms. At a collision energy of 9.5 eV attained in the G-1 and G-11b CRRES releases, the calculations indicate that &sgr;IP=1.3¿10-16 cm2 and &sgr;CE=2--6¿10-16 cm2 for reactions involving Ba(1S20). The cross sections for the analogous Sr reactions are approximately 1.2¿10-16 cm2 and 2--8¿10-17 cm2, respectively. In addition, Sr photoionization from 3PJ metastable states is investigated. Although we calculate a 29-s photoionization time constant from these states, a kinetic analysis indicates the metastable states cannot accumulate an appreciable equilibrium population in full solar exposure. Thus photoionization from the Sr 3PJ levels does not significantly contribute to the total ion inventory. ¿ 1998 American Geophysical Union