Organic photochemistry. 45. Photochemistry of bichromophoric molecules. Intramolecular excited-state interactions in the cis- and trans-decalin-connected aryl olefins: 7-methylene-4b.beta.-methyl-4b.beta.,5,6,7,8,8a.beta.,9,10-octahydrophenanthrene and its 8a.alpha. isomer