Millimeter-wave spectra of the CO dimer: Observation and assignment of 20 new transitions

Over 20 new millimeter-wave transitions of the (CO)-C-12-O-16 dimer are mea sured in the 77- to 186-GHz range using a coaxial pulsed jet spectrometer. Sixteen of these are unambiguously assigned using millimeter-wave combinati on differences, and three are tentatively assigned using infrared data. Som e new or revised assignments of previously observed transitions are also pr oposed. The new results serve to locate a number of levels of the dinner fo r the first time with "microwave" (less than or similar to0.1 MHz) accuracy . Such accuracy is important not just for its own sake, but also because it facilitates future assignments in the CO dimer spectra using precise combi nation differences. (C) 2001 Academic Press.