microARPES and nanoARPES at diffraction-limited light sources: opportunities and performance gains.

The scientific opportunities for microARPES and nanoARPES techniques are discussed, and the benefits to these techniques at diffraction-limited light sources are presented, in particular the impact on spectromicroscopic ARPES (angle-resolved photoemission spectroscopy) of upgrading the Advanced Light Source to diffraction-limited performance. The most important consideration is whether the space-charge broadening, impacting the energy and momentum resolution, will limit the possible benefits for ARPES. Calculations of energy broadening due to space-charge effects will be presented over a wide range of parameters, and optimum conditions for ARPES will be discussed. The conclusion is that spectromicroscopic ARPES will greatly benefit from the advent of diffraction-limited light sources; space-charge broadening effects will not be a limiting factor.