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RISS 인기검색어
- 검색키워드
- 저자 : Moldover, Michael R (검색결과 2 건)
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Determination of the molar mass of argon from high-precision acoustic comparisons
Feng, X J,Zhang, J T,Moldover, M R,Yang, I,Plimmer, M D,Lin, H BUREAU INTERNATIONAL DES POIDS ET MESURES 2017 METROLOGIA -BERLIN- Vol.54 No.3
<P>This article describes the accurate determination of the molar mass <I>M</I> of a sample of argon gas used for the determination of the Boltzmann constant. The method of one of the authors (Moldover <I>et al</I> 1988 <I>J. Res. Natl. Bur. Stand</I>. <B>93</B> 85–144) uses the ratio of the square speed of sound in the gas under analysis and in a reference sample of known molar mass. A sample of argon that was isotopically-enriched in <SUP>40</SUP>Ar was used as the reference, whose unreactive impurities had been independently measured. The results for three gas samples are in good agreement with determinations by gravimetric mass spectrometry; (〈<I>M</I> <SUB>acoustic</SUB>/<I>M</I> <SUB>mass-spec</SUB>〉 − 1) = (−0.31 ± 0.69) × 10<SUP>−6</SUP>, where the indicated uncertainty is one standard deviation that does not account for the uncertainties from the acoustic and mass-spectroscopy references.</P>
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Yang, Inseok,Pitre, Laurent,Moldover, Michael R,Zhang, Jintao,Feng, Xiaojuan,Kim, Jin Seog BUREAU INTERNATIONAL DES POIDS ET MESURES 2015 METROLOGIA -BERLIN- Vol.52 No.5
<P>We determined accurate values of <I>ratios</I> among the average molar masses <I>M</I><SUB>Ar</SUB> of 9 argon samples using two completely-independent techniques: (1) mass spectrometry and (2) measured ratios of acoustic resonance frequencies. The two techniques yielded mutually consistent ratios (RMS deviation of 0.16 ? 10<SUP>−6</SUP> <I>M</I><SUB>Ar</SUB> from the expected correlation) for the 9 samples of highly-purified, commercially-purchased argon with values of <I>M</I><SUB>Ar</SUB> spanning a range of 2 ? 10<SUP>−6</SUP> <I>M</I><SUB>Ar</SUB>. Among the 9 argon samples, two were traceable to recent, accurate, argon-based measurements of the Boltzmann constant <I>k</I><SUB>B</SUB> using primary acoustic gas thermometers (AGT). Additionally we determined our absolute values of <I>M</I><SUB>Ar</SUB> traceable to two, completely-independent, isotopic-reference standards; one standard was prepared gravimetrically at KRISS in 2006; the other standard was isotopically-enriched <SUP>40</SUP>Ar that was used during NIST’s 1988 measurement of <I>k</I><SUB>B</SUB> and was sent to NIM for this research. The <I>absolute</I> values of <I>M</I><SUB>Ar</SUB> determined using the KRISS standard have the relative standard uncertainty <I>u</I><SUB>r</SUB>(<I>M</I><SUB>Ar</SUB>) = 0.70 ? 10<SUP>−6</SUP> (Uncertainties here are one standard uncertainty.); they agree with values of <I>M</I><SUB>Ar</SUB> determined at NIM using an AGT within the uncertainty of the comparison <I>u</I><SUB>r</SUB>(<I>M</I><SUB>Ar</SUB>) = 0.93 ? 10<SUP>−6</SUP>. If our measurements of <I>M</I><SUB>Ar</SUB> are accepted, the difference between two, recent, argon-based, AGT measurements of <I>k</I><SUB>B</SUB> decreases from (2.77 ? 1.43) ? 10<SUP>−6</SUP> <I>k</I><SUB>B</SUB> to (0.16 ? 1.28) ? 10<SUP>−6</SUP> <I>k</I><SUB>B</SUB>. This decrease enables the calculation of a <I>meaningful</I>, weighted average value of <I>k</I><SUB>B</SUB> with a uncertainty <I>u</I><SUB>r</SUB>(<I>k</I><SUB>B</SUB>) ≈ 0.6 ? 10<SUP>−6</SUP>.</P>
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