General Quartic Force Field of CS2

New experimental measurements at high resolution on the ν2 band of CS2 at about 390 cm−1 are reported and analyzed, together with previous data on this molecule, to obtain sufficient vibrational and rotational constants for the calculation of the force constants in the general quartic force field. The well-known Fermi resonance between the vibrational states | υ1, υ2, l2, υ3 〉 and | υ1 − 1, υ2 + 2, l2, υ3 〉 is analyzed taking into account the dependence of the matrix element of the Fermi resonance operator on the rotational quantum number J and on the three vibrational quantum numbers. The anharmonic force constants were determined by least-squares adjustment to the observed spectroscopic data.