Re-evaluation of a precise measurement ofh/m_n

Abstract

At the high-flux reactor of the Institut Laue-Langevin in Grenoble the fine-structure constant was determined by measuring the quotient of the Planck constant and the neutron mass . The results have already been published. In order to evaluate the measurement data, the lattice parameters of several silicon crystals must be known very accurately. As these parameters can now be determined in a more direct way than in the past, the results of the experiment have been re-evaluated. The values obtained by the re-evaluation are (relative standard uncertainty ) and (relative standard uncertainty ), the uncertainties being one-standarddeviation estimates. These values differ from those obtained in the first evaluation by only about 15 % of their uncertainties.

Accurate measurements of the Avogadro and Planck constants by counting silicon atoms

“…A simple example of how this can be done is illustrated by the h/ m( Another example is the h/m(n) = 3.956033285(287) × 10 −7 m 2 /s ratio, whose measurement was completed in 1998 [5][6][7]. This experiment relied on the de Broglie equation m(n)u = h/λ, where both the wavelength λ and the velocity u of monochromatic neutrons were measured.…”

A new photon recoil experiment: towards a determination of the fine structure constant

“…6.7 Photon Recoil h/mCs [6,7] 6.0001(11) 7.7 Quantum Hall effect RK [8,9] 6.0037(33) 24 Neutron Interferometry [10] 6.0015(47) 34 AC Josephson effect Γ ′ p−90 (lo) [11] 5.9880(51) 37 Muonium Hyperfine structure [12] methods can dramatically be reduced in the near future.…”

Spectroscopy of atomic hydrogen

“…In particular, as R ∞ is very well known, it is a link between the fine structure constant α and the h/m e ratio and it is a way to deduce α from the h/m measurements [7,8,9,10]. The next step takes into account the relativistic corrections which are given by the Dirac equation.…”