 For example dissociative adsorption of CO on metal surface (M) is characterized by MC+, MO+, M2O+ and M2C+ secondary ions (Fe and W).And molecular adsorption is identified by MCO+ and M2CO+ ions (Cu, Pd, Ni and Fe).Similarly, it also helps in investigation of binding energy, chemical structure of the adsorbate, interaction between adsorbate molecules and reactivity of adsorbate .