Accurate lineshape spectroscopy and the Boltzmann constant

G.W. Truong, James Anstie, Eric May, T.M. Stace, Andre Luiten

Research output: Contribution to journalArticle

39 Citations (Scopus)
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© 2015 Macmillan Publishers Limited. All rights reserved. Spectroscopy has an illustrious history delivering serendipitous discoveries and providing a stringent testbed for new physical predictions, including applications from trace materials detection, to understanding the atmospheres of stars and planets, and even constraining cosmological models. Reaching fundamental-noise limits permits optimal extraction of spectroscopic information from an absorption measurement. Here, we demonstrate a quantum-limited spectrometer that delivers high-precision measurements of the absorption lineshape. These measurements yield a very accurate measurement of the excited-state (6P1/2) hyperfine splitting in Cs, and reveals a breakdown in the well-known Voigt spectral profile. We develop a theoretical model that accounts for this breakdown, explaining the observations to within the shot-noise limit. Our model enables us to infer the thermal velocity dispersion of the Cs vapour with an uncertainty of 35 p.p.m. within an hour. This allows us to determine a value for Boltzmann's constant with a precision of 6 p.p.m., and an uncertainty of 71 p.p.m.
Original languageEnglish
Article number8345 (2015)
Pages (from-to)1-6
Number of pages6
JournalNature Communications
Publication statusPublished - 14 Oct 2015

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