ROTATIONAL SPECTROSCOPY OF THE COH RADICAL IN ITS GROUND 3-PHI STATE BY FAR-INFRARED LASER MAGNETIC-RESONANCE - DETERMINATION OF MOLECULAR-PARAMETERS

Five rotational transitions of CoH in its ground (3) phi state have been detected by far-infrared laser magnetic resonance, three in the lowest Omega = 4 component and two in the Omega = 3 component. All the Zeeman transitions show an octet hyperfine pattern due to the Co-59 nucleus (I = 7/2). The much smaller proton doubling was also resolved for most transitions. The data have been fitted to experimental accuracy by an effective Hamiltonian for a molecule in an isolated (3) phi state. The electron orbital and spin g factors determined by the data confirm conclusively that the ground state of CoH is a (3) phi state. The accurate measurement of the rotational constant allows the equilibrium bond length to be determined: r(e)= 0.15138435(80) nm. A small Delta-type doubling was resolved in the (3) phi(3) component, suggesting the proximity of a (3) Sigma state among the low-lying electronic states. The cobalt hyperfine splittings have been fitted to determine magnetic dipole and electric quadrupole parameters, which are interpreted in terms of the dominant configuration description for the (3) phi ground state. (C) 1994 Academic Press, Inc.