Thulium trichloride: Thermochemistry of molecular and ionic associates

The composition of saturated vapor over thulium trichloride is studied using the method of high-temperature mass spectrometry. Neutral $(\mathrm{TmCl}_3)_n$ and charged $\mathrm{Cl}$-$(\mathrm{TmCl}_3)_n$ associates up to $n=5$ and $8$, respectively, have been registered for the first time in the temperature range from $868$ to $1110$ K. Partial pressures p(atm) of the vapor components are determined. The second and third laws of thermodynamics are used to calculate the sublimation enthalpies $\Delta_s H^\circ$ ($298$ K) in the form of monomeric and associated molecules, as well as the enthalpies of formation $\Delta_f H^\circ$ ($298$ K) of gaseous molecules and ions.