Measurement of the electronic wave function: Separated atom wave function analysis of the R-dependent hyperfine constants of the iodine monochloride A state

New measurements are presented of the electric and magnetic hyperfine const ants of the I and Cl nuclei for the A((3)Pi (1)) state of (ICl)-Cl-35, nu = 16-27 and 33. This extends the existing set of measurements for the A state to cover most of the vibrational levels from nu =7 to the dissociation lim it. These data are inverted to provide hyperfine constants as a function of internuclear distance. The constants are found to be strongly dependent on the internuclear distance. The changing values are modeled by a separated atom (or valence-bond) model of the wave function. This model contains only eight basis states, but successfully describes the observed changes in the hyperfine constants for internuclear separations ranging from 5.5 down to 2.9 Angstrom. The model also allows the rehybridization of the bond to be d escribed quantitatively as a function of internuclear separation. Two inter esting effects of vibration are observed; first, the orientation of the uno ccupied p orbitals varies considerably over the range of nuclear motion. Se cond, the contribution to the wave function of spin-orbit excited atomic ch lorine states changes dramatically around 3.5 Angstrom. As part of this ana lysis we present extensions to the current methods of estimating molecular hyperfine constants from atomic properties to allow a wider range of parame ters to be covered. <(C)> 2000 American Institute of Physics.