Kinetic Energy Operator for Linear A2B2 Type Molecules in Polyspherical Nonorthogonal Internal Coordinates

The form of the vibrational-rotational operator of kinetic energy for linear symmetric molecules of the A₂B₂ type in polyspherical nonorthogonal internal coordinates (bond lengths and angles between bonds) is obtained. Nonorthogonal coordinates have advantages in calculating the wave functions of heavy linear molecules, for example, C₂F₂ and C₂Cl₂; they also simplify the calculation of the intensity of vibrational-rotational spectral lines of molecules belonging to this type. This work is a continuation of work [1], in which the form of the kinetic energy operator in orthogonal coordinates was obtained. To verify the expressions derived, the lower vibrational-rotational energy levels of the acetylene molecule are calculated.