Autoionization between the ionization thresholds for the 2Π3/2 and 2Π1/2 states of HI+

Abstract

Angle‐resolved photoelectron spectroscopy was carried out on hydrogen iodide using synchrotron radiation. Applying the constant ionic state (CIS) method, studies were made on resonances associated with autoionization between the ionization potential for the two spin‐orbit split lone pair orbitals, π_3/2 and π_1/2. Data on both partial cross sections and angular distribution parameters, β, were obtained for the production of the first ionic state ²Π_3/2 (v=0). These data indicate the presence of several series of Rydberg states leading to the second ionization potential ²Π_1/2 (v=0). Both broad and sharp resonances were observed. A detailed comparison of the data is made with a MQDT calculation in the range of 10.6 to 10.73 eV. Although theory predicts some of the features correctly, there is much room for improvement. Results on the first excited vibrational state [²Π_3/2 (v=1)] are also presented and the effects of vibrational states are discussed.