Partial depolarization effect of high-numerical-aperture objectives on polarized microfocus Raman spectra of orthorhombic poly(oxymethylene) single crystal

microfocus Raman spectroscopic measurement of micron-sized, moth-shaped sin gle crystal of orthorhombic poly(oxymethylene) (metastable phase), the part ial depolarization caused by a sharp focusing with objectives of a high mag nification was investigated in order to obtain the information about the vi brational assignments. Polarized microfocus Raman spectra in the frequency range covering molecular vibrations were compared before and after the intr oduction of an aperture in the collimating system. The spectral difference in the (YX) polarization was observed for the bands of A-B-1 and B-2-B-3 sp lit-pairs, which indicated clearly that the scattering intensities of the B -2 modes as well as the A modes were decreased selectively by the introduct ion of the aperture. In the (XX), (YY), and (XY) spectra, the B-2 modes wer e observed as partial depolarization components of light for electric vecto r component along the depth direction. Utilizing these partial depolarizati on effects, it is possible to assign Raman-active fundamentals and to decid e the unit cell orientation of the micron-sized, moth-shaped single crystal of orthorhombic poly(oxymethylene). Copyright (C) 2000 John Whey & Sons, L td.