Absorption Spectra of NH$_4$MnCl$_3$ and NH$_4$MnF$_3$


The absorption spectra of NH$_4$MnCl$_3$ and NH$_4$MnF$_3$ crystals have been measured down to 10 K in the 250 to 600 nm region. The observed bands are assigned to electronic transitions from the $^6A_{1g}$(S) ground state to various excited levels of Mn$^{2+}$ ions in an octahedral crystalline field. The position of the bands have been fitted within the strong crystal field scheme. Resulting parameters at room temperature are $B = 741$, $C = 2990$ and $Dq = 520$ cm$^{-1}$ for NH$_4$MnCl$_3$ and $B = 800$, $C = 3139$ and $Dq = 694$ cm$^{-1}$ for NH$_4$MnF$_3$. At low temperature some bands show a rich fine structure in which some phonon progressions have been identified.

Solid State Commun. 60, 331–335 (1986)