the target. The difference in the energy δE2 of recoil atoms after collision when two types of atoms differ in their masses by a quantity δM2 is δE2/ δM2 = E0 (dK’/dM2) δE2/ δM2 = 4E0(M1(M1-M2)cos2φ/(M1+M2)2 Mass resolution δMR (≡ δE2/ δM2). A main limitation of using low beam energies is the reduced mass resolution. The energy separation of different masses is, in fact, directly proportional to the incident energy. The mass resolution is limited by the relative E and velocity v. Expression for mass resolution is ΔM = √(∂M/∂E.∆E)2 + √(∂M/∂v.∆v)2 ΔM = M(√((∆E)/E)2+√(2.∆v/v)2) E is the Energy, M is the mass and v is the velocity of the particle beam.and ΔM is reduced mass difference. Multiple scattering scheme in Forward Recoil Spectrometry When an Ion beam penetrating in to matter, ions undergo successive scattering events and deviates from original direction. The beam of ions in initial stage are well collimated(single direction), but after passing through a thickness of Δx in a random medium their direction of light propagation certainly differs from normal direction . As a result, both angular and lateral deviations from the initial direction can occur. These two parameters are discussed below. Hence, path length will be increased than expected causing fluctuations in ion beam. This process is called multiple scattering, and it is statistical in nature due to the large number of collisions. Lateral displacement Case 1 Ion beam fluctuations because of lateral deviations on Target surface is explained by considering Multiple scattering of an ion beam which is directed in x – direction. Angular deviation Case 2 In the below figure there is a considerable difference between in the shape area of Gaussian peak (ideal condition) and angularly deviated peak. and α is an angle due to angular deviation of a penetrated ion beam through matter. Theory and Experimental work involved in Multiple Scattering phenomena In the study of Multiple Scattering phenomenon angular distribution of a beam is important quantity for Consideration. The lateral distribution is closely related to the angular one but secondary to it, since lateral displacement is a consequence of angular divergence. Lateral distribution represents the beam profile in the matter. both lateral and angular Multiple scattering distributions are interdependent. The analysis of Multiple Scattering was started by Bothe(Bothe, W,1921) and Wentzel (Wentzel, G,1922)in the Nineteen twenties using well-known approximation of small angles. The physics of energy straggling and Multiple Scattering