The continued discovery of a wide range of interstellar molecular species is
one of the most exciting aspects of interstellar physics. By 1939 three molecular
species CH, CH', and CN had been detected. The detection of OH in
late 1963 by Weinreb et at. (1963), Bolton et 01. (1 964), Dieter and Ewen (I 964)
ended an almost 25-year lull in the detection of interstellar molecular species
and began the present era of new discoveries. These new discoveries have come
at a time when the conventional view of the interstellar medium was being
challenged on other grounds. A review of molecule formation (McNally,
1968, hereafter called Paper I) based on the conventional model of the interstellar
gas demonstrated the need for good data on reaction rates, photodestruction
rates, radiation fields and other astrophysical constraints