Photoionization of High-Temperature Vapors. VI. S2, Se2, and Te2

Abstract

From the photoionization‐efficiency curves of S₂, Se₂, and Te₂, the thresholds for formation of parent and fragment ions have been determined. The ionization potentials of Se₂ and Te₂ obtained from these measurements are 8.88 ± 0.03 and 8.29 ± 0.03 eV, respectively. For $D_0^0({\mathrm{S}}_2)$ , the value 101.0 ± 0.2 kcal/mole is deduced, in general agreement with other techniques. The result $D_0^0({\mathrm{Te}}_2\text{)\hspace{0.17em}=\hspace{0.17em}62.3\hspace{0.17em}±\hspace{0.17em}0.2}\mathrm{kcal}/\mathrm{mole}$ distinctly favors one of two proposed thermochemical values. The experimental result $D_0^0({\mathrm{Se}}_2\text{)\hspace{0.17em}=\hspace{0.17em}78.6\hspace{0.17em}–\hspace{0.17em}83.2}\mathrm{kcal}/\mathrm{mole}$ has considerable uncertainty but tends to favor the highest of three spectroscopic possibilities. Evidence is presented for a 0.35 ± 0.04‐eV splitting between the $0_g^{+}$ ground state of Te₂ and the $1_g$ state.