Experimental determination of CH-stretching–bending–bending cubic force constants of ethane from Raman intensity analysis

The vibrational anharmonicity of ethane has been experimentally investigated by means of a joint analysis of the gas-phase mean polarizability Raman scattering cross sections and the wave numbers of the multiple vibrational resonances in the C–H or C–D stretching region of several isotopic derivatives. Thirty nine cubic force constants krst in the representation of normal coordinates were obtained in a first step. In a second step they were reduced to a smaller set of isotopically invariant cubic constants Fijk in the representation of curvilinear symmetry coordinates.