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Re-estimation of argon isotope ratios leading to a revised estimate of the Boltzmann constant

2017; IOP Publishing; Volume: 54; Issue: 5 Linguagem: Inglês

10.1088/1681-7575/aa7880

1681-7575

Michael de Podesta, Darren F. Mark, Ross C. Dymock, Robin Underwood, Thomas Bacquart, Gavin Sutton, Stuart Davidson, G. Machin,

Radioactive Decay and Measurement Techniques

In 2013, NPL, SUERC and Cranfield University published an estimate for the Boltzmann constant (de Podesta et al 2013 Metrologia 50 354–76) based on a measurement of the limiting low-pressure speed of sound in argon gas. Subsequently, an extensive investigation by Yang et al (2015 Metrologia 52 S394–409) revealed that there was likely to have been an error in the estimate of the molar mass of the argon used in the experiment. Responding to Yang et al (2015 Metrologia 52 S394–409), de Podesta et al revised their estimate of the molar mass (de Podesta et al 2015 Metrologia 52 S353–63). The shift in the estimated molar mass, and of the estimate of kB, was large: −2.7 parts in 106, nearly four times the original uncertainty estimate. The work described here was undertaken to understand the cause of this shift and our conclusion is that the original samples were probably contaminated with argon from atmospheric air.