Equilibrium constants of Hydrogen and Helium isotopes at low nuclear densities.

Equilibrium constants for hydrogen and helium isotopes as a function of density and temperature are measured in the framework of the study made by Qin et al [2012 Phys. Rev. Lett. 108 172701]. We review and comment on all stages of the analysis and conclude that our measurements are not inconsistent with the results of Qin et al. Improvements are being made to the initial analysis and we raise the issue of the binding energies which has to be clarified.