Results of Fluorescent-Lifetime Studies

RESULTS OF FLUORESCENT-LIFETIME STUDIES A. Introductory Remarks 

As was stated in Sec. I. A, no attempt has been made to include all known measurements of the fluorescent lifetimes of the trivalent rare earths. However, a reasonable effort was made to include a substantial number of the papers on this topic published during the last few years. The criteria of eliminating some papers in which a casual measurement was made was adhered to, and in other cases a language barrier unfortunately prohibited their inclusion. Consequently, this review is representative rather than exhaustive. 

It is convenient to divide the ions studied into four groupings, namely, terbium, europium, neodymium, and other trivalent ions. The reason for this grouping is that terbium, europium, and neodymium have been studied more extensively than the rest, and therefore the number of papers is larger. The greater attention paid to these trivalent ions is probably one of practical or potential practical applications to lasers. 

As would be expected, a number of authors study ions from two or more of these arbitrary groupings in a single paper. Often the techniques used and the results obtained are very similar. This leads in a few instances to some unavoidable repetition in the discussion. 

In the case of two-ion systems, the coupled species is placed into the grouping that corresponds to that ion which has been sensitized. That is, in a system in which energy pumped into, say, gadolinium is fluoresced by, say, terbium, the system is placed into the terbium section. A further subdivision into crystalline solid, glass, and liquid hosts is also made. 

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