Millimeter-wave spectroscopy of PO in excited vibrational states up to v=7

We have measured millimeter-wave transitions of PO, produced by the chemiluminescent reaction of oxygen with white phosphorus, P-4, in excited vibrational states up to v=7. We were hence able to obtain more precise rotational, spin-rotation. Lambda-doubling, and hyperfine constants for this radical and better describe their vibrational dependence. The equilibrium PO bond length was determined as r(e)=1,476 373 55(10)Angstrom. (C) 2002 Elsevier Science (USA).