Singlet-triplet mixing

Singlet-triplet mixing by first-order perturbation theory can now be introduced by two mechanisms ... 

The most recent experimental determination of oAp.ps is that of Al-Ramadhan and Gidley (1994). The apparatus and analysis techniques are similar to those of Westbrook et al. (1989) and will therefore not be described here. Their method used the effect of singlet-triplet mixing in a static magnetic field (Gidley et al., 1982) this allowed oAp-Ps to be... 

Regarding the latter issue, it has to be noticed that for the phosphorescence decay of isolated ligands, the values for rr may be in the ms to sec time range or longer [16]. For the complexes, the heavy atom effect may cause singlet-triplet mixing to an extent that a formal 3LC level exhibits tr as short as tenths of xs [1]. Consistent with this, we shall see later that radiative lifetimes for 3LC emitters of the Ir(III)-polyimine family are tr 50 xs or larger (kt 0.2 x 105 s-1 or smaller, Eq. 2). 

The ZEKE-PFI spectrum, recorded from the HC1 F1 A intermediate state, shows a completely different 2II1/2/2II3/2 subband branching ratio, equal to 0.12 (de Beer, et al., 1990 and Fig. 8.21, upper panel). A calculation, using the BOS formalism (see Section 8.1.1) with ab initio transition moments and a singlet-triplet mixing of 22% reproduces the ratio observed by conventional spectroscopy but not that in the ZEKE spectrum (Fig. 8.21, middle panel). 

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