Raman study of polar phonons in piezoelectric trioxane crystal

摘要

Angular dependence of the Raman bands due to the polar phonons in piezoelectric trioxane crystal was measured at room temperature and at 40 K on singlehyphen;crystal specimens. At room temperature, twoA1bands due to the (A1)8(around 960 cmminus;1) and the (A1)10(480 cmminus;1) modes exhibited remarkable angular dispersion giving the LOndash;TO frequency gaps of 17 and 9 cmminus;1, respectively. For four internal modes of theEspecies,E6throughE9, an appreciable amount of the LOndash;TO splitting, in the range from 4 to 20 cmminus;1, was detected. A remarkable polariton dispersion was also observed for the (A1)8mode. These experimental facts indicated that contribution of the longhyphen;range electrostatic forces produced by the polar modes was significant even in such a molecular crystal.