* This version allows calls to the `spectrum` and `NXspectrum` functions to specify both `sigma` and `gamma` values. If only `sigma` (`gamma`) is given, the crystal field line shape is gaussian (lorentzian). If both values are given, a pseudo-voigt line shape is used, as defined in Ida, Ando and Toraya, J. Appl. Cryst. 33, 1311 (2000).