Chemical Compounds in the Sun.

Sunspot and solar-disk spectrograms, Xx 3000-11500, when compared with laboratory data compiled by Pearse and Gaydon, show that 18 chemical compounds are recognizable in both spot and disk. Criteria for identification are mainly qualitative and physical rather than statistical. Observed vibrational transi- tions are summarized; maximum excitation potentials for spots are well over 1 volt. A finding list of solar bands is given. The compounds NH and probably MgH appear in electronically excited states as well as in the nor- mal state. The red system of CN is weak but extensive in both spot and disk. Newly identified compounds are BH, MgF, SrF, VO, ScO, MgO, and 02, the last being observed in high vibrational levels of the ground term. For 14 others, nearly all considered present by previous observers, no evidence is found. Agreement between abundance estimated from the appearance of bands and computed from~ the theory of dissociative equilibrium by Russell's method is improved and extended