Abstract
In this paper, we report the first rotationally resolved one- and two-color resonance enhanced multiphoton ionization photoelectron spectroscopy (REMPI-PES) study of the HCl molecule. The agreement between our experimental branching ratios and theoretical investigations is excellent. We also report the first zero kinetic energy pulsed field ionization (ZEKE-PFI) experiments carried out in a ‘‘magnetic bottle’’ electron spectrometer. A direct comparison is made between ZEKE-PFI and REMPI-PES spectra for ionization via several rotational levels of the F 1Δ2(v′=0) and f 3Δ2(v′=0) Rydberg states of HCl. Large differences in both the spin–orbit and rotational branching ratios are found between the ZEKE-PFI and REMPI-PES spectra. These differences can be understood qualitatively on the basis of rotational and spin–orbit autoionization mechanisms.