Dissociation Energies of Group VIa Gaseous Homonuclear Diatomic Molecules. II. Selenium

The dissociation energy of Se2(g) has been determined by the simultaneous Knudsen-torsion effusion method. The equilibrium, Se2(g) ⇋ 2Se(g), has been studied with a double-oven, alumina effusion cell; one oven contained elemental selenium and supplied vapor to the hot oven from which the effusion occurred. The value of D0° found in this study is 75.7 ± 2.5 kcal/mole; this value is in excellent agreement with values determined in mass-spectrometric equilibrium studies and in good agreement with a value from a spectroscopic experiment.