Paramagnetic Resonance Absorption ofMn++in Single Crystals of CaCO3

Paramagnetic resonance absorption of ${\mathrm{Mn}}^{++}$ at 9300 Mc/sec has been studied using single crystals of CaC${\mathrm{O}}_3$ containing 0.06 wt. percent ${\mathrm{Mn}}^{++}$ ions. The ${\mathrm{Mn}}^{++}$ spectrum consists of 30 well-resolved lines approximately 3.5 gauss wide and extending over a range of 1100 gauss with a large dependence upon angular orientation between crystal axes and external magnetic field. The theory pertaining to the ${\mathrm{Mn}}^{++}$ resonance absorption in the CaC${\mathrm{O}}_3$ crystal is developed and presented. The interpretation of the observed spectra is based upon crystalline field effects plus nuclear hyperfine interaction. The spectroscopic $g$ factor is found to be essentially isotropic. The hyperfine structure factors $A^{\prime }$ and $B^{\prime }$ are found to be nearly equal. The fine structure constants $D^{\prime }$ and $d^{\prime }$ are determined. The values assigned are: $g_{\mathrm{II}}=2.0022, g_{\perp }=2.0014, A^{\prime }=8.782\mathrm{}\times {10}^{-3\mathrm{}} {\mathrm{cm}}^{-1\mathrm{}},$ $D^{\prime }=3.75\mathrm{}\times {10}^{-3\mathrm{}} {\mathrm{cm}}^{-1\mathrm{}}, d^{\prime }=4.00\mathrm{}\times {10}^{-6\mathrm{}} {\mathrm{cm}}^{-1\mathrm{}}, B^{\prime }=8.774\mathrm{}\times {10}^{-3\mathrm{}} {\mathrm{cm}}^{-1\mathrm{}}.$