Abstract
The electron capture decay of
55Fe was observed with a cryogenic microcalorimeter. The
55Fe source is completely contained in a superconducting tin absorber coupled to a NTD germanium thermistor. The observed spectrum clearly shows the K, L, M capture processes. The M capture shows a clearly resolved peak at 82 eV. The energy resolution was measured with an external
55Fe source to be 35 eV (FWHM) at 6.5 keV.
