Collision, elastic

The molecules are spherical and do not interact with each other except by elastic collisions. Elastic collisions represent no energy loss due to rearrangement of the interior of the molecule. 

Reaction collision Elastic collision Atomic isotope shift... 

It is important to distinguish between two different kinds of collisions elastic and inelastic. As mentioned above, an elastic colUsion is one in which the quantmn states of each atom remain unchanged by the collision. 

Hard sphere elastic cross sections [o.-] have been obtained from averaged molecular force constant as determined from experimental equation of state and transport property data (t6.77). The 2h.2 value for represents the self-collision elastic cross section for Ne. The mixed,values for vs. Hg, Ar and... 

Table 8.2 Degree of conversion of kinetic energy to internal energy for an m/2= 80 ion colliding with an m/z= 16 target molecule as a function of collision elasticity and laboratory reference frame energy (Eu b) of ion...

Particle collisions can be subdivided into two categories elastic collisions and inelastic collisions. Elastic collisions will not change the internal energy of neutral species, but will slightly raise their kinetic energy. With inelastic collisions, the electrical structure of the neutral species will be modified whereby excited species or ions will be created. The lifetime of these species will be very short. Species known as metastables will also achieve an excited state, but also exist with long lifetimes since their decay by radiative emissions is precluded since no energy can be transferred without collisions. 

Figure Bl.24.2. A schematic representation of an elastic collision between a particle of massM and energy Eq and a target atom of mass M2. After the collision the projectile and target atoms have energies of and 2 respectively. The angles 0 and ( ) are positive as shown. All quantities refer to tire laboratory frame of reference.

The identity of target elements is established by the energy of the scattered particles after an elastic collision. The number of atoms per unit area, N, is found from the number of detected particles (called the yield, Y) for a given number Q of particles incident on the target. The connection is given by the scattering cross section a(9) by... 

Figure Bl.24.4. Energy loss components for a projectile that scatters from depth t. The particle loses energy A E- via inelastic collisions with electrons along the inward path. There is energy loss A E in the elastic scattering process at depth t. There is energy lost to melastic collisions A along the outward path. For an incident energy Eq the energy of tlie exiting particle is = q - A iv - AE - A E. ...

Forward recoil spectrometry (FRS) [33], also known as elastic recoil detection analysis (ERDA), is fiindamentally the same as RBS with the incident ion hitting the nucleus of one of the atoms in the sample in an elastic collision. In this case, however, the recoiling nucleus is detected, not the scattered incident ion. RBS and FRS are near-perfect complementary teclmiques, with RBS sensitive to high-Z elements, especially in the presence of low-Z elements. In contrast, FRS is sensitive to light elements and is used routinely in the detection of Ft at sensitivities not attainable with other techniques [M]- As the teclmique is also based on an incoming ion that is slowed down on its inward path and an outgoing nucleus that is slowed down in a similar fashion, depth infonuation is obtained for the elements detected. 

The macroscopic rate coefficient k (cm s for elastic collisions between the ensembles A and B is... 

Both conventions are identical only for direct collisions A (a) + B((3) A(a )+B(P ). This nonnalization is customary [5] for elastic and inelastic scattering processes. 

B-e collisions, then the Bom approximation for atom-atom collisions is also recovered for general scattering amplitudes. For slow atoms B, is dominated by s-wave elastic scattermg so thaty g = -a and cr g = 4ti... 

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