INTERSYSTEM CROSSING RATE CONSTANTS OF RHODAMINE DYES - INFLUENCE OF THE AMINO-GROUP SUBSTITUTION

A time-resolved laser-scanning-microscopy technique is described. Usin g this technique we measured intersystem crossing rate constants of st ructurally related rhodamine dyes. Although rhodamine dyes are disting uished by a low probability of intersystem crossing (< 1%), the result s can be presented with high accuracy. The relationship between the tr iplet quantum yield and molecular structure was investigated. In contr ast to the fluorescence quantum yield, the rate constant of intersyste m crossing is not influenced by the substitution of the amino groups. (C) 1998 Elsevier Science B.V. All rights reserved.