Is the ˜c state of CH2 linear or bent?

The ˜c state of CH₂ is found to be bent at the highest levels of theory used in this work, but the energy difference between the linear and bent geometries is only about 10 cm⁻¹. Improving the basis set or correlation treatment favors the linear geometry over the bent, thus it is impossible to definitively determine if the ˜c state has a barrier in its bending potential. If there is a barrier, it is clear that it will be so small that the ˜c state will be quasilinear. Received: 3 September 1996 / Accepted: 23 September 1996