Determining the location of the low temperature termination of the Frenkel line on the phase diagram

A remarkable and unexpected feature about the Frenkel line as proposed in 2012 is the fact that it demarcates regions on the phase diagram where some fluid properties exhibit liquid-like versus gas-like behaviour, yet does not pass through the critical point. Instead it was proposed to cross the critical temperature at (roughly) 3x the critical density then trend to lower density upon temperature decrease and intersect the vapour pressure curve at 0.75 – 0.8Tc. Whilst experimental works have focussed on the supercritical region, the theoretical proposal that the Frenkel line intersects the vapour pressure curve at 0.75 – 0.8Tc has been challenged by an alternate proposal (from classical molecular dynamics simulations, using nitrogen as an example) that it continues to the vicinity of the triple point. Here, we are therefore making the case for an experiment on subcritical fluid nitrogen at 90 K (0.71Tc) to discover in what region of the Pressure-temperature (P,T) phase diagram the low P,T termination of the Frenkel line lies.