EPR Spectroscopy of Mn2+:CaO An Advanced Physical Chemistry Laboratory Experiment R. Moore', S. G. DiMagno, and H. W. Yoon Swarthmore College, Swarthrnore, PA 19081 Electron naramaenetic resonance (EPR) suectroscouv .. is a powrful t o h in thastudy of the structure and environment of species that rontain unpaired ~lectronn.A number of EPR experimrnta for the undergraduate laboratory ( 1 - 4 have been published in the rhemiral education lirerature. However, no spertroscupir experiment in which a stable paramngneric species with an easily interpretable spectrum is studied has yet been proposed. We have developed an EPR spectroscopy experiment that we have found to be well suited to the undergraduate physical chemistry laboratory. The key feature of the system which we have chosen for study, a powder sample of Mn2+:Ca0, is that the relevant Hamiltonian (5) li = g&H.S
- g&HJ + AS.I
is similar to that for hydrogen2, which is discussed in most nhvsical chemistrv texts. However. the nuclear w i n of Mn2+ is 512, so the EPR spectrum consists of six lin& instead of two. Therefore, the students can interpret the MnZ+spectrum by extension of the concepts that they have learned to understand the hvdroaen spectrum. The spectrum can be described approx
