Photoelectron angular distributions refers to the study of the angular distribution of photoelectrons emitted from a material in response to being irradiated with photons. This research area typically involves using techniques such as angle-resolved photoemission spectroscopy (ARPES) to analyze the energy and momentum of photoelectrons as they are emitted from a material. By studying the angular distribution of these photoelectrons, researchers can gain valuable insights into the electronic structure and properties of materials, such as their band structure and Fermi surface. Photoelectron angular distributions are commonly used in the fields of surface science, condensed matter physics, and materials science to study the electronic properties of materials at a fundamental level.