Knowledge Bank

Accurate measurements of the dipole moment of OH in the v=0.1 and 2 state (1) and of CIO in the v=0 and 1 state (2) are available. Approximation of the electric dipole moment function, M(r), by polynomials in the internuclear separation allows relations between the transition moments and the dipole moments to be derived. A reasonably precise value for the transition moment can be obtained from the dipole moments if the first and second derivatives of M(r) at $r\ast$ are of opposite sign. This is the case for OH but may not be for CIO. For either molecule, the transition moments are not well determined by the present amount of experimental data alone. Ab initio calculations consistently predict certain features of the dipole moment function. The inclusion of these invariant features together with the dipole moment values places bounds on the transition moments. The interaction between vibration and rotation is an important effect in OH (3) and is included in the analysis.