15min:

SANDRO MOLLET AND FRÉDÉRIC MERKT, ETH Zürich, Laboratorium für Physikalische Chemie, Wolfgang Pauli-Strasse 10, 8093 Zürich, Switzerland.

Recently, two studies have been devoted to the low-lying electronic states of Cl₂⁺, one by PFI-ZEKE photoelectron (PE) spectroscopy of the \mathrmX⁺ \mathrmX transition\footnote J. Li, Y. Hao, J. Yang, C. Zhou, and Y. Mo, J. Chem. Phys. \textbf127, 104307 (2007). and one by laser-induced-fluorescence spectroscopy of the \mathrmA⁺ \mathrmX⁺ band system. To complement the information available on the X⁺ and A⁺ electronic states of Cl₂⁺, we have recorded partially rotationally resolved single-photon PFI-ZEKE PE spectra of the \mathrmX^{+ 2} _\mathrmg,i \mathrmX ¹ _\mathrmg⁺ and \mathrmA^{+ 2} _\mathrmu,i \mathrmX ¹ _\mathrmg⁺ (i=3/2, 1/2) photoionizing transitions of Cl₂ in the wavenumber ranges 92 500-96 500 \mathrmcm^-1 and 106 750-115 500 \mathrmcm^-1. These regions correspond to transitions to low-lying vibrational levels of the X⁺ state with v⁺=0-5 and to transitions to vibrational levels of the X⁺ state with v⁺=25-45 and vibrational levels of the A⁺ state with v⁺\leq 7.
The analysis of the rotational structure and the isotopic shifts of these spectra has enabled the derivation of an improved value of the first adiabatic ionization energy (92 647.7\pm0.3 \mathrmcm^-1 for ³⁵Cl₂). In combination with measurements of ion-pair states with n~ 1800\footnote S. Mollet, and F. Merkt, Phys. Rev. A \textbf82, 032510 (2010)., new values for the dissociation energies D₀ of Cl₂ and Cl₂⁺ could also be derived. The potential energy function of the X⁺ state of Cl₂⁺ was determined in a least-squares fitting procedure. Spin-orbit splittings were derived for many vibrational levels of the X⁺ and A⁺ states. Combining our results with other results^b,\footnote R. P. Tuckett, and S. D. Peyerimhoff, Chem. Phys. \textbf83, 203 (1984).^,\footnote L. Wu, X. Yang, Y. Guo, L. Zheng, Y. Liu, and Y. Chen, J. Mol. Spect. \textbf230, 72 (2005).^,\footnote H. van Lonkhuyzen, and C. A. de Lange, Chem. Phys. \textbf89, 313 (1984)., several low-lying vibrational levels of the upper spin-orbit component of the A⁺ state could be assigned for the first time. The PFI-ZEKE PE spectra also contain a series of as yet unassigned lines and reveal numerous perturbations.