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Absolute energies and emission line shapes of the x-ray lines of lanthanide metals



Joseph Fowler, Galen O'Neil, Bradley K. Alpert, Douglas Bennett, Edward V. Denison, William Doriese, Gene Hilton, Lawrence T. Hudson, Young I. Joe, Kelsey Morgan, Daniel Schmidt, Daniel Swetz, Csilla I. Szabo-Foster, Joel Ullom


We use an array of transition-edge sensors, cryogenic microcalorimeters with 4 eV energy resolution, to measure the x-ray emission-line profiles of four elements of the lanthanide series: praseodymium, neodymium, terbium, and holmium. The spectrometer also surveys numerous x-ray standards in order to establish an absolute-energy calibration traceable to the SI for the energy range 4 keV to 10 keV. The new results include: emission line profiles for 97 lines, each expressed as a sum of one or more Voigt functions; improved absolute energy uncertainty on 71 of these lines relative to existing reference data; a median uncertainty on the peak energy of 0.24 eV, four to ten times better than the median for the reference data; and 6 lines that lack any measured values in existing reference tables. The 97 lines comprise nearly all of the most intense L lines from these elements under broad-band x-ray excitation. The work improves on previous measurements with a similar cryogenic spectrometer by the use of sensors with better linearity in the absorbed energy and a gold x-ray absorbing layer that has a Gaussian energy-response function. It also employs a novel sample holder that enables rapid switching between science targets and calibration targets with excellent gain balancing. No energy-dispersive spectrometer has previously been used for absolute-energy estimation at this level of accuracy. Most of the results for peak energy values shown here should be considered a replacement for the currently tabulated standard reference values, while the line shapes given here represent a significant expansion of the scope of available reference data.


X-ray metrology, superconducting transition-edge sensors, microcalorimeters, x-ray fundamental parameters


Fowler, J. , O'Neil, G. , Alpert, B. , Bennett, D. , Denison, E. , Doriese, W. , Hilton, G. , Hudson, L. , Joe, Y. , Morgan, K. , Schmidt, D. , Swetz, D. , Szabo-Foster, C. and Ullom, J. (2021), Absolute energies and emission line shapes of the x-ray lines of lanthanide metals, Metrologia, [online], (Accessed May 10, 2021)
Created January 31, 2021, Updated March 1, 2021