I know that f-f transitions in lanthanides are Laporte and spin forbidden but I don't understand why they are spin forbidden actually... I tried to write it down on a paper but I didn't manage to understand. I used to have problem with d-d spin forbidden transitions so this is maybe why I can't understand it right now...

Thank you in advance!

  • $\begingroup$ See: chemistry.stackexchange.com/questions/105543/… $\endgroup$ Jun 6 at 3:31
  • 2
    $\begingroup$ I don't think f-f transitions are always spin forbidden. The f-orbitals are buried close to the nucleus so they doesn't feel the effect of the ligand, so it's term symbols are not split by the ligand field. There can be excited term symbols with the same spin multiplicity, and that would mean the transition is spin allowed. $\endgroup$
    – S R Maiti
    Jun 6 at 9:06