Transitioning common mistakes

Concerning the luminescence of the lanthanides, the f f transitions are actually described by the spectroscopic levels of the ion, either down to the groimd state or down to an intermediate level. Usually, the visible emissions of the lanthanide ions have transitions that change the total spin number of the ion, i.e., the (2 5 + 1) multiplicity, whereas the NIR emissions do not change the spin. Since several lanthanides exhibit both mechanisms, the term litminescence is preferred over fluorescence or phosphorescence for the lanthanide ions. In this way, the common mistake of calling fluorescence all kind of emissions is avoided. Becatrse of their forbidden character, f-f transitions are slow and the lanthanide luminescence may take up to a few miUiseconds (jns = 10 s). 

Readers may notice the absence of certain terms in common use. The exclusion of some such terms is a deliberate choice. For example, instead of photopeak we prefer full-energy peak we have avoided the statisticians use of error to mean uncertainty and reserve that word to indicate bias or error in the sense of mistake . Branching ratio we avoid altogether. This is often used ambiguously and without definition. In other texts, it may mean the relative proportions of different decay modes, or the proportions of different beta-particle transitions, or the ratio of de-excitation routes from a nuclear-energy level. Furthermore, it sometimes appears as a synonym for gamma-ray emission probabihty , where it is not always clear whether or not internal conversion has been taken into account. 

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