  We report on the fragmentation dynamics of triply charged, diatomic,
molecular ions of NO and CO. Dissociative fragmentation after multiple
ionization of NO and CO is studied under the impact of 200 keV proton beam
using recoil-ion momentum spectrometer. Kinetic Energy Release distributions
(KERDs) for various fragmentation channels were obtained. We have also
calculated the potential energy curves (PECs) for ground and several excited
states of NO^{3+} and CO^{3+} molecular ion. The obtained KERDs are discussed
in the background of the calculated PECs as well as the simple Coulomb
excitation model. Coulomb breakup of the unstable precursor molecular ion shows
a clear preference for the N^{2+} + O^+ (and C^{2+} + O^+) fragmentation
channel.
