Photoselection of Luminescent Molecules in Anisotropic Media in the Case of Two-Photon Excitation. Part II. Experimental Studies of Hoechst 33342 in Stretched Polyvinyl alcohol) Films

Dedicated to Professor Gregorio Weber in the occasion of his 80th birthday It was found by investigating dichroism and emission anisotropy in the case of oneand two-photon excitation of Hoechst 33342 [bis-benzimide,2,5'-bi-lH-benzimidazole, 2'-(4-ethoxyphenyl)-5-5(4methyl-l-piperazinyl)] in stretched poly(vinyl alcohol) (PVA) films, that the absorption and fluorescence transition moments lie along the long molecular axis of the molecule studied. The slight deviation of the transition moment direction in fluorescence (about 8°) from that in absorption can be due to the incomplete linearity of the Hoechst molecule.