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The protonated water dimer irradiated with the free-electron laser FLASH at DESY (90 eV) undergoes Coulomb-explosion after losing one of its valence electrons via photoionization [1]. Because of the close-lying outer valence orbitals and various conical intersections, non-adiabatic effects are presumably important for the overall dynamics. Ab initio potential energy surfaces for the three lowest di-cationic states have been computed at the CASSCF level. A regularized diabatization scheme is used to obtain a diabatic representation of the vibronic Hamiltonian [2]. The quantum dynamics of the photo-fragmentation has been investigated using the multi-configuration time-dependent Hartree (MCTDH) method [3]. We find that the correlation between the motion of the shared proton and the newly created hole builds up in less than five femtoseconds. The build up of the proton-hole correlation is a consequence of strong non-adiabatic effects [4,5].
[1] L. Lammich et al., Phys. Rev. Lett. 105, 253003 (2010).
[2] H. Koeppel, J. Gronki and S. Mahapatra, J. Chem. Phys. 115, 2377 (2001).
[3] M. H. Beck, A. Jaeckle, G. A. Worth and H.-D. Meyer, Phys. Reports 324, 1 (2000).
[4] Z. Li, M. E.-A. Madjet, O. Vendrell and R. Santra, Phys. Rev. Lett. 110, 038302 (2013).
[5] Z. Li. M. E.-A. Madjet and O. Vendrell, J. Chem. Phys., 138, 094313 (2013).
