Numerical Simulations of Multiphoton Processes in Many Electron Atoms
The effects of high intensity, short pulsed lasers on many electron atoms are actively being studied in a number of laboratories. Measurements of ion yields and electron energy and angular distributions as functions of wavelength, intensity and pulse length have provided detailed information about the process of multiphoton ionization. The pulse lengths and intensities currently used are in the regime where standard perturbative methods are invalid. However, direct solution of the time dependent Schrödinger equation for single electron atoms has been shown to be possible.1 In this way, arbitrary pulse shapes can be treated exactly as long as the intensity is high enough that ionization occurs rapidly so that long integration times are not required. In this regime, the highly non-linear process encountered can be accurately described. Extensions of these method are now under development, with applications to the simplest multi-electron atom, helium, having been accomplished.2 In this report, we will present some details of two numerical methods which we have been pursuing for treating the multi-electron case. Both involve a numerical representation of the time dependent Hartree Fock electronic orbitals and a direct time integration of the coupled equations.
KeywordsElectron Atom Lawrence Livermore National Laboratory Multiphoton Ionization Alternate Direction Implicit Method Time Dependent Schrodinger Equation
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- 3.D. Gottlieb, M. Y. Hussaini and S. A. Orszag, “Theory and Applications of Spectral Methods” in Spectral Methods for Partial D. Differential Equations, ed. by R. G. Voigt, D. Gottlieb and M. Y. Hussaini, SIAM publications (Philadelphia, 1984).Google Scholar