Quadrupole Effects in Core and Valance Photoelectron Emission From Crystalline Germanium Measured Via a Spatially Modulated X-Ray Interference Field

Published

April 1, 2002

Author(s)

E J. Nelson, Joseph C. Woicik, P Pianetta, I A. Vartanyants, J W. Cooper

Abstract

Near an x-ray Bragg reflection, two x-ray beams (incident and reflected) with opposite wavevectors exist within the crystal to create an x-ray standing wave (XSW) interference field. The part of the photoelectron yield depending on quadrupole (and higher order non-dipole) transitions will differ for these two beams, because of the dependence of the quadrupole cross-section on the angle between photon wavevector and photoelectron direction. By monitoring the photoelectron yield as a function of photon energy along the back-reflected direction in an XSW field near the (11-1) Bragg backreflection condition of crystalline Ge, we measure the contribution of non-dipole effects to Ge 3p, Ge 3d, and Ge valance (4p) photoelectron emission. Significant changes due to non-dipole emission are measured in both the apparent amplitude and phase of the Ge structure factor relative to the true Ge atomic distribution. Calculated atomic quadrupole asymmetry parameters for photoelectron emission from the Ge core levels and valance band are found to agree with the parameters extracted from our measured photoelectron yields.

Citation

Physical Review B (Condensed Matter and Materials Physics)

Volume

65

Issue

No. 16

Pub Type

Journals

Keywords

non-dipole interactions, x-ray interference field, x-ray photoelectron spectroscopy, x-ray standing waves

Citation

Nelson, E. , Woicik, J. , Pianetta, P. , Vartanyants, I. and Cooper, J. (2002), Quadrupole Effects in Core and Valance Photoelectron Emission From Crystalline Germanium Measured Via a Spatially Modulated X-Ray Interference Field, Physical Review B (Condensed Matter and Materials Physics) (Accessed October 13, 2025)