Millimeter-Wave Spectra of the CO Dimer: Three New States and Further Evidence of Distinct Isomers

✍ Scribed by Jian Tang; A.R.W. McKellar; L.A. Surin; D.N. Fourzikov; B.S. Dumesh; G. Winnewisser

• Publisher: Elsevier Science
• Year: 2002
• Tongue: English
• Weight: 160 KB
• Volume: 214
• Category: Article
• ISSN: 0022-2852
• DOI: 10.1006/jmsp.2002.8579

✦ Synopsis

The millimeter-wave spectrum of the normal isotope of the CO dimer, ( 12 C 16 O) 2 , has been systematically surveyed in the regions 75-105 and 131-174 GHz, with additional measurements covering the entire 60-176 GHz range. By combining these results and using the technique of combination differences based on previously known energy levels, 14 new rotational levels have been assigned and precisely (≈0.1 MHz) located. They belong to 3 completely new states, 1 with A + symmetry and 2 with A -symmetry. The position of the lowest energy A -state results in a new and lower value for the effective tunneling splitting of the CO dimer, 3.73 cm -1 . The observation of dramatically different intensities for different bands supports the concept of two isomeric forms for (CO) 2 , the ground state having a larger intermolecular separation (≈4.4 A ❛ ) with most likely a C-bonded configuration, and the low-lying (0.88 cm -1 ) excited state having a smaller separation (≈4.0 A ❛