Moreover, following a calibration technique used in earlier measurements ATOMIC AND MOLECULAR PHYSICS, on C +60with SRMS2 at DESIRS [3], we were able to derive absolute DILUTE MATTER, UNIVERSE SCIENCE values for the photoionization cross sections of the studied PAH cations. SYNCHROTRON SOLEIL HIGHLIGHTS 2020 Together with theoretically calculated photoabsorption cross sections from time-dependent density functional theory (TD-DFT), we determined the photoionization yield of our PAH cations. DESIRS BEAMLINE FIGURE 2 Associated publication Astrochemical relevance of VUV ionization of large PAH cations. G. Wenzel, C. Joblin, A. Giuliani, S. Rodriguez Castillo, G. Mulas, M. Ji, H. Sabbah, S. Quiroga, D. Peña, L. Nahon. Astronomy & Astrophysics, 641: art. n° A98 (2020). References ASTROPHYSICAL IMPLICATIONS AND CONCLUSIONS [1] C. Joblin etal. , J. Phys.: Conf. Ser., 1412, 062002 (2020). Thanks to these experiments, we were able to produce molecular data [2] J. Montillaud et al., A&A, 552, and recipes of use for astrophysical models. The first recipe concerns A15 (2013). an empirical law for the evolution with size and charge of the ionization [3] S. Douix et al., J. Phys. Chem. Lett., potentials. It was fitted from the appearance energies (AE) of the dicationic 8, 7−12 (2017). (and tricationic) PAHs complemented with earlier measurements on smaller [4] J. Zhen et al., ApJ, 822, 113 (2016). PAHs with SRMS2 at DESIRS [4] as well as ionization potentials (IP) [5] H. W. Jochims et al., A&A, 314, 1003–1009 (1996). computed using DFT. Additionally, we parametrized the photoionization yield to formulate a photoionization yield equation for PAH cations which Corresponding author could be compared to the equation deduced earlier for PAH neutrals ([5] and Figure 3). This equation is our second astrophysical recipe, Christine Joblin (/Gabi Wenzel) describing the crucial parameter of photoionization as a function of IRAP, Université de Toulouse (UPS), photon energy and depending on the molecular size of the PAH. Both CNRS, CNES, 9 Avenue du Colonel astrophysical recipes can be readily used in chemical models that Roche, 31028 Toulouse, France christine.joblin@irap.omp.eu describe the chemical evolution of PAHs in astrophysical environments. FIGURE 3 Captions FIGURE 1: Schematic of the different possible relaxation processes of PAHs upon absorption of a VUV photon in star-forming regions and involved characteristic molecular timescales. Scheme adapted from [1]. Credit for the original image of NGC 7023 to Hubble/ESA. FIGURE 2: Molecular structures and photoionization branching ratio relative to photodissociation as a function of photon energy, for (a) benzobisanthene, C32H14, (c) DBPP, C36H18, and (d) dicoronylene,, C30H14, (b)+ ovalene + + CH+4820, after absorption of a single VUV photon. FIGURE 3: Photoionization yields for PAH cations, Y+i , (this work) and neutrals, Y, (from [5]) estimated for 34, 48,on and 60 carbon atoms. 63