Molecular absorption of chemical species in flames has been observed by some workers. These works have been done from a spectroscopic or analytical point of view. So far, molecular absorption of alkali halides in the flames has received extensive attention, because their absorption in the uv region causes a significant background absorption interference for atomic absorption analysis of many atoms. As for alkaline earth compounds, molecular absorption of CaOH and SrO in the visible region has been investigated in the air-acetylene flame, and also is considered to cause background absorption interference in the analysis of Ba, Li, Na, and Cr. However, no study on flame absorption spectra of alkaline earth compounds except for MgCl has been reported in the uv region.
Etsuro Yoshimura, Naoki Furuta, Hiroki Haraguchi, and Keiichiro Fuwa, "Molecular Absorption Spectra of Strontium Halides in Air-Acetylene Flame," Appl. Spectrosc. 31, 560-562 (1977)