Neon: the fitted model

The neon model (fit/Ne): the 73.6 nm and 74.4 nm resonance lines at their NIST energies and two effective oscillators, with the magnetic susceptibility \(\chi_0 = -8.48\times10^{-5}\) a.u. The level comes from Lesiuk, Przybytek & Jeziorski’s ab initio Cauchy moments and Gaiser & Fellmuth’s 2018 dielectric static polarizability (via Lesiuk; their 2010 value is 16 ppm higher); the shape from the Cuthbertsons’ visible data (level free: their standard state is ambiguous, and it comes out 0.3 % high) and Bideau-Mehu’s vacuum ultraviolet.

The fit’s reduced chi-squared is 2.5: the experiments’ dispersion is about 0.6 % stronger, relative to the static term, than the ab initio S(-4) allows (TC-92), as the refractivity-constrained distributions of Kumar & Thakkar and of Langhoff & Karplus also show; the band is scaled by the reduced chi-squared. Birch (+0.14 %), Orcutt & Cole (+0.33 %) and Leonard’s compilation (+0.27 %) lie high, like the classical helium values.

from _helpers import fit_overview

fig = fit_overview("Ne", xlim=(70e-9, 20e-6))