The Morse oscillator‐rigid bender internal dynamics (MORBID) Hamiltonian [P. Jensen, J. Mol. Spectrosc. 128, 478 (1988)] has been used in a fitting to all extant rotation–vibration data for X 3B1 methylene CH2. This fitting leads to an improved determination of the potential energy surface, and in particular to reliable predictions for the stretching frequencies. We predict ν1=2992 cm−1 and ν3=3213 cm−1 for 12CH2, and we hope that the new predictions will encourage the experimental search for these weak fundamentals. In the MORBID approach the rotation–vibration energies are obtained from the potential energy surface in a purely variational calculation, and consequently the present work is an improvement over previous determinations of the CH2 potential energy surface from experiment that used the nonrigid bender formalism [see P. R. Bunker et al., J. Chem. Phys. 85, 3724 (1986), and references therein]; this latter approach treats the stretching vibrations by second order perturbation theory. A fitting ...

The potential surface and stretching frequencies of X̃ 3B1 methylene (CH2) determined from experiment using the Morse oscillator‐rigid bender internal dynamics Hamiltonian

Flexible models for intramolecular motion, a versatile treatment and its application to glyoxal☆

A new morse oscillator-rigid bender internal dynamics (MORBID) Hamiltonian for triatomic molecules

Selected one‐electron properties for eight small molecules (H2O, CO, N2, H2S, NH3, PH3, HCl, and HF) have been computed using extended Gaussian basis sets at the SCF and CI levels. The basis sets and CI methodologies were capable of recovering approximately 86% of the estimated total correlation energy (88% of the valence) and, to the best of our knowledge, yielded the lowest variational energies and closest overall agreement with experimentally determined properties to date. Compared to numerical Hartree–Fock properties the current values are generally within 1%, with the largest deviation being 2.6% for δ at the nucleus. The sensitivity of the computed properties to the basis set composition and type of CI are discussed.

A.R. Hoy

Papers

The effective rotation-bending Hamiltonian of a triatomic molecule, and its application to extreme centrifugal distortion in the water molecule