Contents 5 APPROXIMATION METHODS 285 5.1 Time-Independent Perturbation Theory: Nondegenerate case 285 5.2 Time-Independent Perturbation Theory The Degenerate Case 298 5.3 Hydrogenlike Atoms:Fine Structure and the Zeeman Effect 304 54 Variational Methods 313 55 Time-Dependent Potentials:The Interaction Picture 316 5.6 Time-Dependent Perturbation Theory 325 5.7 Applications to Interactions with the Classical Radiation Field 335 341 345 6 IDENTICAL PARTICLES 357 357 Symn 8 6.4 The Helium Atom 366 6.5 Permutation Symmetry and Young Tableaux 370 Problems 377 7 SCATTERING THEORY 379 7.1 The Lippmann-Schwinger Equation 379 7.2 The Born Approximation 386 7.3 Optical Thec em 390 74 Eikonal Approximation 7.5 Free-Particle States:Plane Waves Versus Spherical Waves 395 7.6 Method of Partial Waves 399 77 Low-Energy Scattering and Bound States 7.8 Resonance Scattering 418 7.9 Identical Particles and Scattering 42 7.10 Symmetry Considerations in Scattering 422 7.11 Time-Dependent Formulation of Scattering 424 7.12 Inelastic Electron-Atom Scattering 7.13 Coulomb Scattering Problems 441 Appendix B Appendix C Supplement I Adiabatic Change and Geometrical Phase Supplement II Non-Exponential Decays 481 graphy 487 Index 491