The electronic spectroscopy and photochemistry of the trans isomers of 3-(N-phenylamino)stilbene (nil 3-(N-methyl-N-phenylamino)stilbene (m1d), 3-(NN-diphenylamino)stilbene (nille), and 3-(N-(2,6-dimethylphenyl)amino)stilbene (m1f) and their double-bond c