Effect of hot bands on the ionization threshold of some diatomic halogen molecules

Abstract

Photoion-yield curves are obtained for the molecular ions of the homonuclear diatomic halogens and for iodine monochloride and iodine monobromide. Excepting iodine, ionization thresholds of ground-state and vibrationally-excited molecules are separately identified by measurements made at several ion-source temperatures. The adiabatic ionization energies (in eV) are: I(F 2 = 15.69, I(Cl 2) = 11.48, I(Br 2) = 10.52, I(ICl) = 10.07, and I(IBr) = 9.79. A preferred value of I(I 2) = 9.37 eV is proposed.