Ab initio configuration interaction determination of the overtone vibrations of methyleneimine in the region 2800–3200 cm−1

Ab initio configuration interaction (CI) potential function calculated from a 6-311G** basis set at a MP2 level of theory is used to compute the vibrational energy levels of methyleneimine CH2NH between 2800 and 3200 cm−1. The most important configurations selected by an iterative process by means of a variational perturbational method are diagonalized. Results show a perfect agreement with the most reliable experimental values and predict the ν5+ν6, ν4+ν6, and ν4+ν5 unobserved combinations.