HYPERFINE-STRUCTURE OF PENDULAR STATES AND THE SIGN OF THE DIPOLE-MOMENT OF ICI-A-STATE

Since a first study by Cummings and Klemperer [J. Chem. Phys. 60, 2035 (1974)] and further works by Friedrich and Herschbach, the dipole mom ents of the X and A states of ICI are considered to have opposite sign s. We have performed a high resolution study of the Stark effect of th e A -X transition near the 21-0 bandhead, and we have made a complete theoretical simulation of the spectrum, taking into account the hyperf ine structure which is important. The comparison of the experimental s pectrum with the simulation clearly prove that the dipole moments of t he A and X state have the same sign. This result is in agreement with simple electronegativity arguments.