Relativistic Theoretical Study On Photoionization And Radiative Recombination

The basic task of atomic and molecular physics is to research the atomic structure, property and interaction regularity. It came from the study of sun spectrum and gas discharge at 19 century. After the first developmental peak of 1930s', it turned into independent physical branch.Think of the transformation condition of Maxwell equations and the character of electric, magnetic field, the meaning of wave function for free radiative field is showed by solving the equations. Golden rule may be obtained by perturbation theory, it is one of the most important inclusions in quantum theory and the basic theory to study the microcosmic atomic transition process. If the final wavefunction of photoionization is normalized on the energy scale, Golden rule would be simpler.The calculation of transition matrix element is the center aim on studying the interaction between atom and radiative field, but its general expression is very complex. Adopted further theoretic approximation, the expression of matrix element will be more abbreviated.It is a essential task to solve Schrodinger(or Dirac) equation with refined and reasonable Hamilton of atomic and molecular physics. For an atom containing N electrons, if N>l,exact solution can't be found at all and approximations of one sort or another are required. Some early theoretic methods are successful to research photoionization as well as its inverse, but it can't catch up with the development of atomic and molecular physics. Multi-configuation Dirac-Fock(MCDF) is a relativistic theory method, the interelectronic correction is taken into account by the choice of configuration state functions. During the past 30 years, the development of MCDF is very rapidly, at the present time it can deal with complex atom.The cross section shows the chracteristic of photoionization and its inverse, so photoionization and its inverse are usually researched with the cross section.By the principal of detailed balance, the radiative recombination cross section of single-electron systems have been calculated with photoionization. The result showthat the important factors what influenced the cross section of radiative recombination of single-electron systems are principal quantum number n , angular quantum number l,atomic core, Z and so on. These factors can influence the mean distance between ionized electron and nucleus, orbital shape, effective nuclear charge what electron felt, so influence the nuclear Coulomb potential and wave function indirectly, and ultimately influenced the transition matrix element, makes it possible that the cross section of radiative recombination change more or less. When the kinetic energy of free electron decrease to zero continuously, The variation of RR cross section with electron kinetic energy will go into complexity: Cooper minimum, the variation would change non-monotonously. Cooper minimum isn't the continuum state by origin, but sign change of transition matrix element, it is a universal character of photoionization or its inverse for atom and molecule and likely to occur in the cross section for outer-shell photoionization or its inverse of high_ and intermediate_Z element.