English: The f→d promotion energies for the f‐elements (bar across figure is estimate of
crystal energy needed to compensate for promotion of an electron from an f to a d level ).
{{Information |Description=The f→d promotion energies for the f‐elements (bar across figure is estimate of crystal energy needed to compensate for promotion of an electron from an f to a d level ). |Source={{cite book|first = Richard G.|last = Hair...