Ion Implantation and Synthesis of Materials - Studium

1.5 Energy and Particles 721 2 c2F = Z Zekr,(1.7)where the Coulomb law constant k c = ¼ πε 0 = 8.988 × 10 9 m F −1 in the SI system(where 1 F ≡ 1 A s V −1 ) and is equal to unity in the cgs system.The conversion factor follows from:2 −19 2 9 −1 −28 2 −1ekc = (1.6× 10 C) × 8.988 × 10 m F = 2.3×10 C m F .The conversions 1 C ≡ 1 A s and 1 J ≡ 1 C V lead to the units of the farad:1 F ≡ 1 A s V –1 ,so that2.31= 2.31× 10 C m F = eV nm = 1.44eV nm.1.62 −28 2 −1cek9 282 −1 2 1 910 J nm 101C mF ≡ −1C Vm(As) ≡ 1J m ≡ 10 J nm ≡ eVnm−19 −1(1.6 × 10 J eV )= 1.6andIn this book we will follow the cgs units for e 2 with k c = 1, so thate2= 1.44eV nm.(1.8)Each nucleus is characterized by a definite atomic number Z and mass numberA; for clarity, we use the symbol M to denote the atomic mass in kinematicequations. The atomic number Z is the number of protons, and hence the numberof electrons, in the neutral atom; it reflects the atomic properties of the atom. Themass number gives the number of nucleons (protons and neutrons); isotopes arenuclei (often called nuclides) with the same Z and different A. The current practiceis to represent each nucleus by the chemical name with the mass number as asuperscript, e.g., 12 C. The chemical atomic weight (or atomic mass) of elements aslisted in the periodic table gives the average mass, i.e., the average of the stableisotopes weighted by their abundance. Carbon, for example, has an atomic weightof 12.011, which reflects the 1.1% abundance of 13 C.The masses of particles may be expressed as given in Table 1.1 in terms ofenergy through the Einstein relationE = Mc 2 , (1.9)