Unlike octadecyl-tethering hemicyanine (HC-18), nonyl-tethering hemicyanine (HC-9) entered the hydrophobic channels of silicalite-1 with a very small preference to the inclusion with the alkyl part first.Accordingly, while the degree of uniform orientation (DUO) of HC-18 in the channels was 0.67, that of HC-9 was only 0.08.This phenomenon was ascribed to the fact that HC-9 has a hydrophilic part at the center and two hydrophobic parts on both sides with almost equal hydrophobicities.Upon irradiation of the HC-9 dyes oriented parallel to the channel direction of silicalite-1 on the surface of the silicalite-1 film at 5 °C with a laser beam derived from an Ar+-ion laser (488 nm, 1.6 W), the DUO of the included HC-9 increased to 0.27.This phenomenon was attributed to the inclusion of HC-9 into the silicalite-1 channels in the excited-state in accordance with the phenomenon that the hydrophilic center shifts to the very end of the mol. (di-Me amino group) in the excited state, giving rise to lengthening of the relatively hydrophobic region.