The study of the rates and processes of chemical reactions is known as chemical dynamics. It also includes the investigation of the energy exchange that takes place when molecules collide in gaseous or condensed phase conditions. The chemical identity and energy content (i.e., electronic, vibrational, and rotational state populations) of the interacting species must thus be able to be monitored by the experimental and theoretical techniques employed to study chemical dynamics. Additionally, because the speeds of chemical reactions and energy transfer are crucial, these instruments must be able to function on the time scales over which these frequently extremely rapid processes occur. Let's start by looking at several of the theoretical models that are most frequently used to simulate and comprehend the processes.