Abstract
The hyperfine coupling constant (A in units of energy or Aβ² in units of magnetic field) and zeroβfield splitting (D in units of energy or Dβ² in units of magnetic field) in the ESR spectrum of Mn^2+^ in calcite were determined. The spreading of the nonβcentral allowed transitions |3/2, mγ β |5/2, mγ, |1/2, mγ β |3/2, mγ, |β3/2, mγ β |β1/2, mγ and |β5/2, mγ β |β3/2, mγ was analysed and the experimental transitions were attributed. Particular relevance was given to the difference between the two types of resonances, shoulder or divergence, and to their origin (M, m). The analysis explains the presence of a weak shoulder between each of the five central doublets |β1/2, mγ β |1/2, mγ. Six independent methods for calculating the hyperfine coupling constant and five methods for calculating the zeroβfield splitting, based on the analysis of the allowed and forbidden transitions, were provided. The values of the hyperfine coupling constant range from β93.9 to β94.6 G and those of the zeroβfield splitting range from β79.5 to β80.5 G. A critical evaluation of the advantages and drawbacks of the 11 methods is included: the best value for Aβ² is β94.30 G and that for Dβ² is β79.95 G. Copyright Β© 2005 John Wiley & Sons, Ltd.