Coincidence ion pair production (cipp) spectroscopy of halogen molecules Bálint Sztáray 1 , Kristján Matthíasson 2 , Gustavo A. Garcia 3 , Peter Weidner 1 , Ágúst Kvaran 2, * 1 University of the Pacific, United States, 2 University of Iceland, Iceland, 3 Synchrotron SOLEIL, France Coincidence ion pair production (cipp) spectroscopy uses an experimental setup that is identical to Photoelectron Photoion Coincidence (PEPICO) spectroscopy, but cation-anion pairs are detected instead of electron-cation pairs. Our cipp measurements on fluorine (F 2 ) and iodine (I 2 ) were recorded on the DELICIOUS III coincidence spectrometer of the Soleil Synchrotron in France. 1 The cation/anion coincidence signals showed rotational band head structures, corresponding to F 2 or I 2 Rydberg states crossing over to the ion pair production surface above the ion pair production limit. Spectral simulation and quantum defect analysis allowed characterization of the Rydberg states for both systems. In fluorine, the lowest-energy Rydberg state spectrum observed lacked some of the predicted rotational structure, which allowed an accurate determination of the ion pair production threshold, which led to the most accurate ground state F–F dissociation energy. 2 PEPICO experiments were also carried out on F 2 and the dissociative photoionization threshold further confirmed the cipp-derived F 2 bond energy. For I 2 , the analysis revealed a number of previously unidentified states and a reassignment of others following a discrepancy in previous assignments. 3 References 1. Tang, X. F.; Garcia, G. A.; Gil, J. F.; Nahon, L. Vacuum upgrade and enhanced performances of the double imaging electron/ ion coincidence end-station at the vacuum ultraviolet beamline DESIRS. Rev. Sci. Instrum. 2015 , 86. 2. Matthiasson, K.; Kvaran, A.; Garcia, G. A.; Weidner, P.; Sztaray, B. Resolving the F-2 bond energy discrepancy using coincidence ion pair production (cipp) spectroscopy dagger. Phys. Chem. Chem. Phys. 2021 , 23, 8292-8299. 3. Matthíasson, K.; Kvaran, Á; Garcia, G. A.; Weidner, P.; Sztáray, B. Coincidence Ion Pair Production (cipp) Spectroscopy of Diiodine. Phys. Chem. Chem. Phys. 2022 , submitted.
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