15min:

CHRISTOPHER F. NEESE, JENNIFER L. GOTTFRIED AND TAKESHI OKA, Department of Chemistry, Department of Astronomy & Astrophysics, and the Enrico Fermi Institute, The University of Chicago, Chicago IL, 60637, USA.

The molecular ion CH₂⁺ is of special theoretical interest because it is both quasi-linear and exhibits a strong Renner-Teller interaction between its ground and first-excited electronic states. At linearity, the ground state is a ² _u state that splits into X²A₁ and A²B₂ states as the molecule bends. The A state is linear, while the X is quasi-linear with a barrier to linearity of only 1089~cm^-1. Thus, only the ground vibrational state is bound by the barrier to linearity.

The spectrum of CH₂⁺ in the region 11,000--13,000~cm^-1 has been recorded with our Ti:sapphire laser spectrometer. This spectrometer couples velocity modulation with heterodyne detection for near shot-noise-limited sensitivity. Since our initial letter on this spectrum, we have selectively rescanned portions of this spectrum with improved signal-to-noise. As a result, we have been able to assign the A(0,3,0)³ X(0,0,0)² band and detect the X(0,9,0)² X(0,0,0)¹ band, whose assignment is in progress. A more detailed analysis of the entire spectrum, including spin splitting, is underway.