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.