Double‐valence photoionization of SUVA134a molecule (CFH₂CF₃)

Abstract

In this work we investigate the single-photon double ionization of the SUVA 134a (1,1,1,2-tetrafluoroethane) molecule in the energy range from 21.21 to 320 eV. Our experimental data are supported by Thomas' and Samson's models. It is shown that the double photoionization of the SUVA 134a can be expressed as a sum of the so-called shake-off (SO) and the knockout (KO) processes. Methods:The experiments were executed at the TGM beamline at Laborat orio Nacional de Luz Síncrotron in Campinas, Brazil. The source of EUV and X-ray radiation was a bending magnet that enabled us to work in the photon energy range of 21.21 to 320 eV. The spectrometer was devised to collect 100% of the ions with kinetic energies up to 30 eV. The photoelectron-photoion (PEPICO) and photoelectron-photoion-photoion (PE2PICO) coincidence techniques were used in the present work. Results:The ratio of double-to-total photoionization as a function of the photon energy for the SUVA molecule exhibits remarkably similar behavior with other atomic and molecular systems. SO depends on large excess energy above the ionization threshold, enabling the photoelectron to leave the interaction region rather speedily to yield a sudden change in the Coulomb field that the shaken electron feels. The measured asymptotic SO probability is P SO (∞) = 0.09. Conclusions:The present analysis shows that the separation of SO and KO processes relies on the experimental evidence that there is no significant interference between SO and KO. The analysis also shows that the separate formulation of KO and SO presents a factual portrayal of double photoionization.Despite having 50 electrons, SUVA has lower double-to-total photoionization fraction (9%) in comparison, for instance, to argon atoms ($20%), which has 18 electrons. This lower e-e correlation could be attributed to its larger volume, that is, lower electron density. | INTRODUCTIONAt low photon energies (EUV), photo-double ionization of atoms and molecules is a rare event, corresponding to only a small percentage when compared to single ionization. It can take place either directly or indirectly. Photo-double ionization of atoms and molecules by a single photon is a central many-body process. Direct double ionization is portrayed by a single photon absorption by the target followed by the sudden ejection of two electrons, as opposed to sequential or indirect core ionization or excitation followed by a series of Auger decays, or