In contrast, these values of BTD-HeBr in T1 and T2 is as low as 0.10% and 0.00%, respectively. These results indicate that the contribution of the excited state wave function of bromine is greatly reduced through the spatial heavy atom strategy, resulting to distinctly low nonradiative decay. In addition, the non-radiative transition from T1 to S0 is another important deactivation route of the triplet exciton. The knr(T1→S0) was calculated using the following equation :