Absorption spectra of matrix-isolated alkaline earth metal diatomic molecules

Mg, Ca, and Sr atoms were codeposited with argon and krypton at 10 K for optical absorption investigation of the van der Waals diatomic molecules. Very strong and weak structured absorptions were observed for Mg2 at 367 and 444 nm, respectively. An unstructured 507 nm and a strong structured 648 nm absorption were found for Ca2, and a strong structured 710 nm absorption was observed for Sr2. Intermediate absorptions with intermediate spacings were observed for CaMg, SrMg, and SrCa in mixed-metal experiments. The strong absorptions are assigned to 1Σ+u(1S+1P) ←1Σ+g(1S+1S) transitions.