Raman Effect of Acetylenes. I. Methyl-, Dimethyl- and Vinyl-Acetylene

An improved helical discharge tube containing neon and mercury with a saturated solution of sodium nitrite as filter served as a monochromatic source of radiation (4358 Hg). A mechanical filter avoided overexposure of the exciting radiation. The vibration frequencies were studied on the basis of the symmetry properties of the molecules and the usual assignments have been made. Faint rotation lines were found accompanying the C $⋮$ C vibration in liquid dimethyl‐acetylene. They are interpreted as rotation of the six hydrogen atoms around the figure axis of the molecule. The moment of inertia is I = 10^—39 g×cm². The three compounds were studied in the liquid state.