Thermochemical properties of gaseous Li2 and Li3

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Using the Knudsen effusion mass spectrometric technique, the gas species Li(g), Li2(g), and Li3(g) have been observed over liquid lithium. The atomization energies of Li2(g) and Li3(g):D0° (Li2) =25.5±1.5 kcal/mole and D0° (Li3) =41.5±4.0 kcal/mole, were derived from the study of the various gaseous equilibria: Li(s,l) →Li(g) (1), 2Li(s,l) →Li2(g) (2), Li2(g) →2Li(g) (3), 3Li(s,l) →Li3(g) (4), 2Li2(g) →Li3(g)+Li(g) (5). The following heats of formation were also obtained: ΔH0° (Li) =38.5±1.0 kcal/mole, ΔH0° (Li2) =51.5±2.0 kcal/mole, ΔH0° (Li3) =73.0±4.0 kcal/mole. The ionization potentials of Li2 and Li3 were determined as 4.86±0.1 and 4.35±0.2 eV, respectively, from which the binding energies D0° (Li+2) =37.7±2.0 and D0° (Li+3) =65.5±4.3 kcal/mole result.