title: Dissociation and multiple ionization energies for five polycyclic aromatic hydrocarbon molecules.
abstract: We have performed density functional theory calculations for a range of neutral, singly, and multiply charged polycyclic aromatic hydrocarbons (PAHs), and their fragmentation products for H-, H(+)-, C(2)H(2)-, and C(2)H(2)(+)-emissions. The adiabatic and vertical ionization energies follow linear dependencies as functions of charge state for all five intact PAHs (naphthalene, biphenylene, anthracene, pyrene, and coronene). First estimates of the total ionization and fragmentation cross sections in ion-PAH collisions display markedly different size dependencies for pericondensed and catacondensed PAH species, reflecting differences in their first ionization energies. The dissociation energies show that the PAH(q+)-molecules are thermodynamically stable for q ≤ 2 (naphthalene, biphenylene, and anthracene), q ≤ 3 (pyrene), and q ≤ 4 (coronene). PAHs in charge states above these limits may also survive experimental time scales due to the presence of reaction barriers as deduced from explorations of the potential energy surface regions for H(+)-emissions from all five PAHs and for C(2)H(2)(+)-emission from naphthalene--the smallest PAH.
authors.affiliation: Department of Physics, Stockholm University, SE-106 91 Stockholm, Sweden.
authors.forename: A I S
authors.initials: AI
authors.lastname: Holm
authors.forename: H A B
authors.initials: HA
authors.lastname: Johansson
authors.forename: H
authors.initials: H
authors.lastname: Cederquist
authors.forename: H
authors.initials: H
authors.lastname: Zettergren
mesh_terms: D000873:Anthracenes / Q000737:chemistry; D001713:Biphenyl Compounds / Q000737:chemistry; D002244:Carbon / Q000737:chemistry; D006859:Hydrogen / Q000737:chemistry; D007477:Ions / Q000737:chemistry*; D009281:Naphthalenes / Q000737:chemistry; D011084:Polycyclic Aromatic Hydrocarbons / Q000737:chemistry*; D011083:Polycyclic Compounds / Q000737:chemistry; D011721:Pyrenes / Q000737:chemistry; D011789:Quantum Theory; D013816:Thermodynamics
chemical_list: D000873:Anthracenes; D001713:Biphenyl Compounds; D007477:Ions; D009281:Naphthalenes; D011084:Polycyclic Aromatic Hydrocarbons; D011083:Polycyclic Compounds; D011721:Pyrenes; C031721:naphthalene; D002244:Carbon; D006859:Hydrogen; C012256:coronene; C030984:pyrene; C034020:anthracene