  We use narrow spectral lines from the x-ray spectra of various highlycharged
ions to measure low-energy tail-like deviations from a Gaussian
responsefunction in a microcalorimter x-ray spectrometer with Au absorbers at
energiesfrom 650 eV to 3320 eV. We review the literature on low energy tails in
othermicrocalorimter x-ray spectrometers and present a model that explains all
thereviewed tail fraction measurements. In this model a low energy tail arises
fromthe combination of electron escape and energy trapping associated with Bi
x-rayabsorbers.
