  Detector counting rate nonlinearity, though a known problem, is commonly
ignored in the analysis of angle resolved photoemission spectroscopy where
modern multichannel electron detection schemes using analog intensity scales
are used. We focus on a nearly ubiquitous "inverse saturation" nonlinearity
that makes the spectra falsely sharp and beautiful. These artificially enhanced
spectra limit accurate quantitative analysis of the data, leading to mistaken
spectral weights, Fermi energies, and peak widths. We present a method to
rapidly detect and correct for this nonlinearity. This algorithm could be
applicable for a wide range of nonlinear systems, beyond photoemission
spectroscopy.
