Vibration-rotation polarizability operator for nonlinear X2Y-type molecules and the rovibrational Raman cross-section calculation of water molecules

The expression for the second - order transformed polarizability operator for non-linear X2Y -type molecules is derived using the method of contact transformation. This operator is used for the calculation of ro-vibrational Raman cross sections of the H2O molecule. It is shown that the ro-vibrational correction terms change the integral intensity of pure rotational lines significantly and the ν2 band slightly. The vibrational dependence of the mean polarizability of H2O is analyzed in the calculation of integral intensity of one and two quantum bands.