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^-1, are used to probe the photodissociation dynamics and bond strength of the manganese oxide cation (MnO⁺). These studies confirm the theoretical ground state (⁵Π) and determine the spin-orbit constant ( A' = 14 cm^-1) of the dominant optically accessible excited state (⁵Π) in the region. Photodissociation via this excited ⁵Π state results in ground state Mn⁺ (⁷S) + O (³P) products. At energies above 30,000 cm^-1, the Mn⁺ (⁵S) + O (³P) channel is energetically accessible and becomes the preferred dissociation pathway. The bond dissociation energy ( D₀ = 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.