The equilibrium geometry, potential function, and rotation-vibration energies of CH2 in the X̃ 3B1 ground state

Abstract

By fitting the eigenvalues of the nonrigid bender Hamiltonian to the 26 available experimental rotation‐vibration energy level splittings of the ³B₁ ground electronic state of the methylene radical CH₂ we determine the equilibrium geometry and potential function; the data only involve rotational transitions and transitions in the ν₂ bending fundamental band. From the fit we determine that the equilibrium bond length is 1.075 Å, the equilibrium bond angle is 133.9° and the height of the barrier to linearity is 1878 cm⁻¹. We are able to use the nonrigid bender Hamiltonian, with this potential, to predict all the lower rotation‐vibration energy levels, including the ν₁ and ν₃ band origins, of CH₂ and its isotopes.