MICROOPTICAL SPECTROSCOPY OF B1I(3) MOLECULES ADSORBED IN NANO-CHANNELS OF ZEOLITE SINGLE-CRYSTALS

Absorption spectra are reported for BiI3 molecules incorporated into c hannels of zeolite MOR and AFI. Polarized absorption spectra for the z eolite single crystals, of size about 50 mu m, were measured by means of microoptical spectroscopy. The absorption spectrum of BiI3 in MOR i s different from that observed in LTA, and also shows a polarization d ependent on the direction of the channel. The BiI3 molecule is expecte d to have nearly C-3v symmetry even in the MOR channels, and has a pre ferred orientation of the molecular axis along the channel. On the oth er hand, no polarization dependence of BiI3 is observed in the AFI cha nnel, although AFI has a channel size similar to that of MOR. The cati ons and the framework induce the electric field inside the MOR channel s, which acts as an adsorption potential for molecules. The experiment al results indicate that the electric field plays an important role in the molecular orientation.