## Abstract

A relativistic model for the extended x-ray-absorption fine structure, in which the energy loss of the emitted photoelectron is accounted for by using a complex energy-dependent exchange-correlation potential, has been developed. Relativistic curved-wave single-, double-, and triple-scattering formulas for excitation from any core hole have been found. The dominant single-scattering signal has been computed for the first shell at the L2 and L3 edges of Th (Z=90), Pt (Z=78), and Eu (Z=63) and at the K edge of Sr (Z=38) using this model. Comparisons of the relativistic scattering amplitudes of the Dirac model with the current standard Schrödinger curved-wave model reveal that the latter deviates from the more exact Dirac model by 20% above 240 eV for Th, by 15% above 240 eV for Pt, and by 10% above 140 eV for Eu. For lower energies, the deviations are as much as two times larger. Differences between the Dirac model L2- and L3-edge amplitudes occur below 240 eV for Th and Pt with values of 2% and 6%, respectively. For Eu, this difference diminishes to 4% and occurs only below 140 eV. In the case of the K edge of Sr, the Schrödinger single-scattering amplitude differs from the Dirac amplitude by 5% for energies above 95 eV. The spin dependence of the generalized Ramsauer-Townsend effect is also exhibited.

Original language | English (US) |
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Pages (from-to) | 12578-12589 |

Number of pages | 12 |

Journal | Physical Review B |

Volume | 49 |

Issue number | 18 |

DOIs | |

State | Published - Jan 1 1994 |

Externally published | Yes |

## All Science Journal Classification (ASJC) codes

- Condensed Matter Physics