15min:
THE A(0,8,0)1 leftarrow X(0,0,0)2 AND A(0,8,0)3 leftarrow X(0,0,0)2 BANDS OF CH2+.

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 methylene 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 Piu state that splits into X2A1 and A2B2 states as the molecule bends. The A state is linear, while the X state is quasi-linear with a barrier to linearity of only 1089~cm-1.

Recently, the spectrum of CH2+ in the region 10,700--11,000~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. In this new spectrum we have assigned the A(0,8,0)1 leftarrow X(0,0,0)2 and A(0,8,0)3 leftarrow X(0,0,0)2 bands. These bands are the first high-resolution detection of Ka=2 levels for the ground state. In addition, the A(0,8,0)1 leftarrow X(0,0,0)2 can be combined with the previously studied A(0,8,0)1 leftarrow X(0,0,0)0 band to produce Ka= 2-0 combination differences for the ground state. These combination differences provide the first high-resolution information about the ground state A rotational constant.