Photoionization of High-Temperature Vapors. I. The Iodides of Sodium, Magnesium, and Thallium

Abstract

A vacuum‐ultraviolet monochromator, a mass spectrometer, and a molecular‐beam source of high‐temperature vapors have been combined to obtain photoionization efficiency curves of high‐temperature species. In the TlI system, the ions Tl⁺, I⁻, and TlI⁺ were observed. Two independent threshold processes yield 2.77₀ and 2.76₉ eV for D₀(TlI). The ions Na⁺, NaI⁺, Na₂I⁺, Na₂I₂⁺, and Na₃I₂⁺ were detected in NaI vapor. The threshold for Na⁺ yields 3.00 eV for D₀(NaI). No negative ions were observed in NaI vapor. The ions MgI₂⁺ and MgI⁺ were measured in MgI₂ vapor, the latter providing a basis for estimates of the energies for successive removal of I atoms from MgI₂. The ionization potentials of TlI, NaI, Na₂I₂, and MgI₂ are found to be 8.46₉, 7.64, 7.64, and 9.57 eV, respectively.