In one most preferred embodiment, the dye is N N {HEAD ~ 3,3,3,3 tetramnethylbenzindodicarbocyanine}, which has {TAIL ~ the formula}: ##STR3## 
has
In one most preferred embodiment , the dye is N N { HEAD ~ 3,3,3,3 tetramnethylbenzindodicarbocyanine } , which has { TAIL ~ the formula } : # # STR3 # #
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH