Recoil cross section

The absolute precision of ERS therefore depends on that of da/dfl (Ej, (t>). Unfortunately, some disagreement prevails among measurements of the recoil cross section. One recent determination is shown in Figure 4a for (t> = 30° and 25°. The convergence of these data with the Rutherford cross section near 1 MeV lends support to their validity. The solid lines are least squares fits to the polynomial form used by Tirira et al.. For (t> = 30°, the expression reads ... 

For atomic masses M2 4 Mj the recoil cross-section is almost independent of the atomic number, because the cross-section becomes proportional to (Z2/M2) and the ratio Z2/M2 is close to 0.5 for all elements. ERDA with heavy projectiles thus has the advantage of almost constant sensitivity for all elements. Only for hydrogen the ratio Z2/M2 is equal to 1, hence the intensity of hydrogen recoils is enhanced by roughly a factor of four. 

For quantitative evaluation of ERDA energy spectra considerable deviations of recoil cross-sections from the Rutherford cross-section (Eq. 3.51) must be taken into account. Light projectiles with high energy can penetrate the Coulomb barrier of the recoil atom the nuclear interaction generally leads to a cross-section that is larger than ctr, see Eq. (3.51). For example, the H recoil cross-section for MeV He projec-... 

Reasonable estimates of ultimate sensitivity and depth resolution in ERDA can hardly be given because of the large range of projectiles and energies (from He ions of several MeV up to 200-MeV Au ions), and the use of different detection systems. In addition, stability of the sample under irradiation (which, of course, depends on the target material) is also important in the discussion of sensitivity and detection limits. The sensitivity is mainly determined by the recoil cross-section, the solid an-... 

Theorists calculate cross sections in the CM frame while experimentalists usually measure cross sections in the laboratory frame of reference. The laboratory (Lab) system is the coordinate frame in which the target particle B is at rest before the collision i.e. Vg = 0. The centre of mass (CM) system (or barycentric system) is the coordinate frame in which the CM is at rest, i.e. v = 0. Since each scattering of projectile A into (v[i, (ji) is accompanied by a recoil of target B into (it - i[/, ([) + n) in the CM frame, the cross sections for scattering of A and B are related by... 

The elastic cross sections for scattering and recoil in the Lab-frame are related to the cross section in the CM-frame by... 

Because the cross-sections for nuclear reaction are usually lower than the cross-sections for elastic scattering of projectiles used in RBS or in elastic recoil detection analysis (ERDA), higher currents must be used to obtain comparably high intensity in... 

Normally these conditions are satisfied in fast highly charged ion-atom collisions. From Eq. (66) we can derive the equations for the singly differential cross sections with respect to the components of the longitudinal momentum distributions for the electron, recoil-ion, and projectile. The longitudinal electron momentum distribution da/dpe for a particular value of p, may be derived by integrating over the doubly differential cross section with respect to the electron energy Ek ... 

After several decades of systematic electron spectroscopy in ion-atom collisions by many groups (for recent reviews see Refs. 13 and 51), there are only two data sets of doubly differential experimental cross sections cfa/dE dfl for the emission of electrons with < 1 eV. It has been only recently that, with entirely new and extremely efficient electron spectrometers combined with recoil-ion momentum spectroscopy [52], doubly differential cross sections for ultralow -and low-energy electrons (1.5 meV < < 100 eV) have been obtained by... 

Figure 14. Double differential cross sections (ddcs — 2n dv v J for electron emission due to single, double, or triple ionization of Ar by 3.6-MeV/amu Au53+ ions. The DDCS for the specified recoil-ion charge states are added according to their relative contribution to the total cross section. CDW-EIS results (solid lines [73]) are shown along with the experimental data from Moshammer et at. [53], The experimental data are divided by 1.4. Cross sections at different ve are multiplied by factors of 10, respectively.

One of the most promising applications of polyboron hydride chemistry is boron neutron capture therapy (BNCT) for the treatment of cancers (253). Boron-10 is unique among the light elements in that it possesses an unusually high neutron capture nuclear cross section (3.8 x 10-25 m2,0.02—0.05 eV neutron). The nuclear reaction between 10B and low energy thermal neutrons yields alpha particles and recoiling lithium-7 nuclei ... 

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