Evidence for speed-dependent effects in NH3 self-broadened spectra: towards a new determination of the Boltzmann constant

Meriam Triki (1) , Cyril Lemarchand (1) , Benoît Darquié (1) , Papa Lat Tabara Sow (2) , Vincent Roncin (1) , Christian Chardonnet (1) , Christophe Daussy (1)

1 LPL - Laboratoire de Physique des Lasers
2 hotes

In this paper we present an accurate analysis of the shape of an isolated rovibrational ammonia line from the strong nu2 band around 10 µm, recorded by laser absorption spectroscopy. Experimental spectra obtained under controlled temperature and pressure, are confronted to various models that take into account Dicke narrowing or speed-dependent effects. Our results show clear evidence for speed-dependent broadening and shifting, which had never been demonstrated so far in NH3. Accurate lineshape parameters of the nu2 saQ(6,3) line are obtained. Our current project aiming at measuring the Boltzmann constant, kB, by laser spectroscopy will straight away benefit from such knowledge. We anticipate that a first optical determination of kB with a competitive uncertainty of a few ppm is now reachable.

Mots clés: laser spectroscopy; absorption lineshape; fundamental constants

Domaines: Physique Quantique [quant-ph]

Meriam Triki, Cyril Lemarchand, Benoît Darquié, Papa Lat Tabara Sow, Vincent Roncin, et al.. Evidence for speed-dependent effects in NH3 self-broadened spectra: towards a new determination of the Boltzmann constant. Physical Review A : Atomic, molecular, and optical physics [1990-2015], 2012, 85 (6), pp.062510. ⟨10.1103/PhysRevA.85.062510⟩. ⟨hal-00661417⟩