Determination of derivatives of the polarizability anisotropy in diatomic molecules

The effect of vibration-rotation interaction on the intensities of Raman spectra of diatomic molecules is investigated. We use a numerical approach to diagonalize the vibration-rotation matrix. It is shown that perturbation theory is not adequate for molecules with large rotational constants, such as H2 and D2. For heavier molecules, such as N2 and O2, deviations are found between the numerical and perturbation calculations when the rotational quantum number is large. Six anharmonic potential constants are determined for hydrogen, and four for nitrogen.