Consequently, it is possible to estimate kTTA using the exact same measurements that was used to determine tT ( = 1/kT) of the annihilators. An additional benefit is that it is now possible to directly relate Ith and b. Since b is evaluated at [ 3 ASS], Ith is the excitation intensity that yields b = 0.5. Ith may, thus, be estimated from only a few measurements of the UC emission decay in which the excitation intensity is varied to yield values of b slightly above and below 0.5.