Oblique phonons in uniaxial molecular crystals: Raman spectra of s ‐trioxane

Using Raman scattering the angular dispersion of extraordinary phonons in s ‐trioxane, a uniaxial crystal of trigonal structure, has been measured. It has been found that the transitions are of the type TO → LO or LO → TO so that the anisotropic short‐range forces predominate over the long range electrostatic ones. The LO–TO splittings are of the order of 10 cm −1 or less as expected for molecular crystals. For phonon propagation direction along the optic axis extraordinary and ordinary phonons of E species coincide.