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On Wed, October 10, 2007 11:50 am, Bryan W. Lepore wrote: > On Wed, 10 Oct 2007, Jim Pflugrath wrote: >> It has come to my attention that the wavelength of a Copper Kalpha may >> have changed over the years. At least this appears to be true if you >> look at the International Tables. > > the 'natural' isotopic distribution must have changed, as it has with the > biggest example lithium, since the 'nuclear age' - i take that to be the > principal reason. > > and i take it that everyday-use copper anodes are isotopically impure? > > -bryan > The change was probably around 1967, when the meter was defined, slightly, using krypton. Tungsten was used as a reference, and the kX to A ratio was changed: Bearden, Rev Mod Phys, 39, 78 (1967). old values from IT, volume III alpha-1 1.54051 alpha-2 1.54433 beta-1 1.39217 beta-2 1.38102 alpha 1.54178 the ratio of I(alpha-2)/I(alpha-1) = 0.497 the units are kX/1.00202, and good to 1 in 25,000, based on kX, for 1962 (IT, 1962). newer values, from IT, volume IV alpha-1 1.540562 alpha-2 1.544390 beta-1 1.392218 beta-5 1.38109 based on the W K-alpha-1 line/peak at 0.2090100 A Bernie Santarsiero