Comparison of Experimentally Derived and Theoretically Calculated Derivatives of the Energy, Kinetic Energy, and Potential Energy for CO

Abstract

Theoretical values of the energy, kinetic energy, and potential energy obtained recently by approximate Hartree—Fock calculations by Nesbet for N₂, CO, and BF have been used to obtain values of the derivatives of these quantities. Using equations obtained by differentiation of the virial‐theorem expression for diatomic molecules and experimental values of B_e, ω_e, ω_ex_e, and α_e, experimental values of the derivatives of E, T, and V have also been obtained. The probable accuracy of the power‐series expansions in internuclear separation which are used to represent the computed energy values is considered, as is the choice of the value of the internuclear separation at which the derivatives are evaluated. The experimentally derived and theoretically calculated derivatives are compared. A corresponding comparison of derivatives of the energy of CO and BF is made using the results of the more elaborate approximate Hartree—Fock calculations reported by Huo. It is shown from Nesbet's data that potential constants obtained from derivatives of the kinetic energy or potential energy are as precise as those obtained from derivatives of the energy.