Magnetic circular dichroism of the 1S→1P transition of Mg atoms in noble gas matrices

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Abstract
A magnetic circular dichroism (MCD) and absorption study has been made of the 1S (3s2) →1P (3s3p) transition of Mg atoms in Ne, Ar, Kr, and Xe matrices. Triplet structure is observed in the latter three, and a detailed analysis of the MCD shows that this structure results from a splitting of the 1P excited state at a single site. An analysis of the zeroth and first MCD and absorption moments shows that the orbital angular momentum of this 1P state is partially quenched, the quenching factors being approximately 0.65, 0.75, 0.50, and 0.43 in Ne, Ar, Kr, and Xe matrices, respectively. This quenching is necessarily a consequence of out‐of‐state mixing (i.e., orbital mixing outside the atomic 1P excited manifold) and almost certainly reflects strong mixing of the 3p Mg orbitals with noble gas orbitals on neighboring host atoms. An analysis of higher absorption and MCD moments assuming octahedral site symmetry shows a dominant noncubic (Jahn–Teller active) mode contribution to the bandwidth in the three hosts in which the triplet structure is resolved. This suggests a Jahn–Teller explanation of the triplet structure not only for Mg but also for other atoms in noble gas matrices whose S →P transitions show the same general pattern. This pattern is characteristic of the T1×t2g Jahn–Teller case.