THE NEUTRAL AND IONIC COMPONENTS OF SATURATED VAPOR OF SAMARIUM DICHLORIDE - THE THERMOCHEMICAL CHARACTERISTICS OF GASEOUS MOLECULES AND IONS

High-temperature mass spectrometry is used to investigate the composit ion of saturated vapor of samarium dichloride in the temperature range of 1037-1303 K. It is found that SmCl2 molecules provide the dominant component of vapor. Small amounts of SmCl3 molecules are also detecte d. The pressure of saturated vapor of samarium dichloride is determine d. The second and third laws of thermodynamics are applied to determin e the enthalpy of sublimation of samarium dichloride Delta(s)H degrees (SmCl2, 298 K) = 341 +/- 8 kJ/mol. The enthalpy of formation of gaseou s molecule of SmCl2 Delta(f)H degrees(SmCl2, g, 298 K) = -462 +/- 8 kJ /mol is calculated. The ionic component of equilibrium vapor is studie d for the first time, which is represented by positive and negative io ns such as Sm+, SmCl+, Sm2Cl2+, Sm2Cl3+, Sm2Cl4+, Sm3Cl5+, Cl-, SmCl3- , SmCl4- Sm2Cl6-, and Sm2Cl7-. The equilibrium constants of ion-ion an d ion-molecule reactions are measured, and the enthalpy of reactions a nd enthalpy of formation of recorded ions are calculated by the third law of thermodynamics. The values of electron affinity are estimated f or SmCl3 molecules and SmCl4 radical, which are respectively equal to 2.5 +/- 0.2 and 5.1 +/- 1.0 eV.