Recoil particles

In TOF-SARS [9], a low-keV, monoenergetic, mass-selected, pulsed noble gas ion beam is focused onto a sample surface. The velocity distributions of scattered and recoiled particles are measured by standard TOF methods. A chaimel electron multiplier is used to detect fast (>800 eV) neutrals and ions. This type of detector has a small acceptance solid angle. A fixed angle is used between the pulsed ion beam and detector directions with respect to the sample as shown in figure Bl.23.4. The sample has to be rotated to measure ion scattering... 

For accurate ion trajectory calculation in the solid, it is necessary to evaluate the exact positions of the intersections of the asymptotes (A A2) of the incoming trajectory and that of the outgoing trajectories of both the scattered and recoiled particles in a collision. The evaluation of these values requires time integrals and the following transfonnation equations ... 

TOF-SARS and SARIS are capable of detecting all elements by either scattering, recoiling or both teclmiques. TOF peak identification is straightforward by converting equation (Bl.23.lt and equation (B 1.23.81 to the flight times of the scattered and recoiled particles as... 

Because RBS is rather insensitive to light elements and unable to detect hydrogen, one can make use of the complementary technique Elastic Recoil Detection (ERD) when sensitivity for light elements is required. In this case, recoiled particles are detected instead of the back scattered particles. The incident beam usually consists of heavier ions, e.g. 2 Si (4He is sufficient when one is interested in H and D only), and a stopper foil prevents backscattered particles from entering the detector, whereas the lighter recoiled particles are transmitted [32]. 

Q.) is based on the ejection of the recoiled particles out of the sample in the forward direction by an energetic heavy ion beam. The measured energy spectra of these recoiled atoms can be related to their concentration profiles. The use of range foil in front of the energy detector to permit selective absorption of the various recoils introduces a few limitations in the application of the technique, e.g. deterioration of the energy resolution and hence the depth resolution, the limitation on the accessible depth in the depth profile information, etc. Indeed, the practical utility of the experimental set-up is enormously reduced in the region where overlapping spectra of various atoms are difficult to separate. 

Physics. Lithium, beryllium, boron, sodium, and a number of other elements, each have an isotope that, upon capturing a thermal neutron, undergoes an exoerglc reaction. These reactions produce energetic charged particles, either a proton or an alpha particle depending upon the isotope, and a recoil particle. Each particle emitted has a specific kinetic energy defined by the Q-value of the reaction which in turn serves to identify the element. For the case of lithium. 

The outgoing recoiling particle j (proton or deuteron) recoiling from site a is represented by a plane wave, exp(i p Raj), with momentum p = p -I- q, where p is its initial momentum in its bound state in the material. 

Energy transfer from a projectile to a target nucleus in an elastic two-body collision - concept of kinematic factor (K = E2/E0 i.e., ratio of energy of the recoiled particle to the energy of the incident particle)... 

The energy fraction transferred from primary to recoil particles is given by the kinematic factor for recoiling ... 

It is clear from the figure that the energy of the recoil particle is maximal when Ml = M2. Further, it is clear from (3.3) and (3.4) as well as Fig. 3.2 that for M2/M1 > 1, the kinematic factor for scattering (Ag) for the scattered incident particles is larger than the kinematic factor for recoiling (Aj.) and increases with increasing mass ratio. 

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