In order to study the mol. orientation of brilliant yellow (BY) and methyl orange (MO) in black soap (cationic surfactant) films with resonance Raman spectra, three-point datum collection method (collecting polarized Raman scattering intensity data at three point, i.e., two datum line points and one peak point) was set up to measure the polarized ratios of the -N=N- stretching vibration band at various incident angles. The theor. relations were discussed between the two ratios and the incident angle for the uniaxial orientation model and orientation distribution model,resp. By fitting the experimental data of the polarized ratios with the uniaxial orientation model, it was discovered that BY was laid down the interface of black soap films (tilt angle ~80? and the tilt angle of MO decreased from 70?to 65?when the black soap film took the gel-to-liq. crystal phase transition. From the fitting results with the orientation distribution model, the orientation distribution graphs of the long axis of the azo dyes were given. BY and MO were mainly laid down the film plane, but there were some orientation probabilities in other directions, and the gel-to-liq. crystal phase transition resulted in a decrease in the orientational order of MO.

Key words: RAMAN SPECTROMETRY, MOLECULAR ORIENTATION