One of the mechanisms that has been proposed to explain the phenomenon of sudden sodium layers (SSLs) in the upper atmosphere is dissociative attachment of electrons to sodium compounds such as NaHCO3 and NaCO3. In this study, ab initio calculations have been used to estimate the reaction enthalpies (ΔH¿0(NaX+e- →Na+X-) for NaHCO3 and NaCO3, which are found to be 72¿20 (0.75) and 21¿30 (0.22) kJ mol-1 (eV), respectively. NaHCO3 is then shown to be relatively stable above the mesopause. This property, together with its rather small threshold for dissociative electron attachment, makes NaHCO3 a possible source of SSLs under certain conditions. ¿ American Geophysical Union 1993