We can understand the vibronic contributions by looking at the three mechanisms composing the singlet-triplet transition dipole moment in Eq. . Figure shows the contributions of each of these mechanisms to the singlet-triplet transition dipole for BA, MeBA, MoBA, and DMABA. The solid line in each graph marks the value for the T1 minimum, while the histogram tells the NEA contributions (whose mean value is indicated by the dashed line). These vertical values are collected in Table .