Photofragment Imaging, Spectroscopy, and Theory of MnO.

Density functional and ab initio calculations, along with photodissociation spectroscopy and ion imaging of MnO from 21,300 to 33,900 cm, are used to probe the photodissociation dynamics and bond strength of the manganese oxide cation (MnO). These studies confirm the theoretical ground state (Π) and determine the spin-orbit constant ( A' = 14 cm) of the dominant optically accessible excited state (Π) in the region. Photodissociation via this excited Π state results in ground state Mn (S) + O (P) products. At energies above 30,000 cm, the Mn (S) + O (P) channel is energetically accessible and becomes the preferred dissociation pathway. The bond dissociation energy ( D = 242 ± 5 kJ/mol) of MnO is measured from several images of each photofragmentation channel and compared to theory, resolving a disagreement in previous measurements. MRCI+Q calculations are much more successful in predicting the observed spectrum than TD-DFT or EOM-CCSD calculations.