Photoionization mass spectrometry of HI and DI at high resolution

The ionization potentials of HI and DI to the 2Π3/2 and 2Π1/2 states are redetermined by extrapolation of Rydberg series seen in photoionization, as: I.P.(HI), 2Π3/2=10.386±0.001 eV, 2Π1/2 =11.0495±0.001 eV; I.P.(DI), 2Π3/2=10.387±0.001 eV, 2Π1/2 =11.0505±0.001 eV The spin-orbit parameter A(HI) =−0.664±0.002 eV. Several new Rydberg series have been identified and the first vibrationally excited levels have been located in three of the 2Π states. The spectra of HI and DI are discussed and are contrasted with the photoionization spectrum of atomic Xe. Changes in the relative shapes and intensities of Rydberg peaks as functions of n* are ascribed to changes in angular momentum coupling schemes.