Angular distributions of photoemission in hard X-ray photoelectron spectroscopy using linearly polarized light

Characterizing the angular distributions of photoemission is important for evaluating the elemental composition of materials by hard X-ray photoelectron spectroscopy (HAXPES; HX-PES). These distributions cannot be explained by dipole approximation, and their parameters have been theoretically derived using non-dipole approximation. In this study, the angular distributions of photoelectrons emitted from 3s, 4s, 4p, 4d, and 4f states, observed directly using the HAXPES analyzer with a wide angle objective lens, were investigated by irradiating 8 keV X-rays onto a platinum (Pt) surface. In the 4d and 4f states, the obtained distributions were asymmetric relative to the X-ray polarization vector. This asymmetry was consistent with theoretical results using the non-dipole approximation. Thus, the angular distributions of photoemission predicted by non-dipole approximation were experimentally confirmed at various energy levels of Pt.