1. Electronic Spectroscopy of 1-Methylpyrene cation and related species. D. Kokkin, C. Marshall, A. Bonnamy, And C. Joblin and A. Simon

2. The Unidentified Infra Red (UIR) bands Infrared emission features that match the vibrational modes of the polycyclic aromatic hydrocarbons (PAHs) Must survive UV radiation field conditions

3. The Diffuse Interstellar Bands Series of absorption bands between 400 nm and about 1400 nm Observed in both galactic and extra-galactic sources Primarily in diffuse sources but weakly observed in dense clouds http://bjm.scs.uiuc.edu/research/opb2.php

4. Properties of the DIBs UV flux seems important: Too little or too much UV removes the DIB absorbers IRC+10216 vs IRAS06530-0213 Chemical composition of local environment important Some DIBs show structure: Isotopic? Rotational? Sarre, MNRAS 277, 1995

5. Why 1-Methylpyrene cation? Léger, A., D’Hendecourt, L., & Défourneau, D. (1995), A&A, 293, L53 1- Methylene pyrene or related photo product possible carrier for indicated DIBs from matrix spectra.

6. The Experiment – FTICR-MS The PIRENEA-Setup Cold ICR cell Technique validated in the work of Useli Bacchitta et al in obtaining the optical spectra of isolated PAH cations by resonant multi-photon dissociation Useli Bacchitta et al. 2010 chem Phys, 371,16

7. The PIRENEA set-up for astrochemistry UV-Visible irradiation Superconductor magnet (5T) ICR cell Turbo-molecular pump OPO laser 210 nm – 2 µm Solid pellet Ablation laser (266 nm) External cold shield Internal cold shield z r P ~ 10 -11 mbar T=35 K

8. 8 Absorption of UV photon - Relaxation mechanims IV. NRT, PAH et MIS ~10 -12 s 10 -2 - 1 s From short timescales (~ps) to very long timescales (~s)

9. Ion trap + MPD technique Advantage:  production in situ of isolated cations in various hydrogenation state  provide good band position for the gas-phase ion  oscillator strength derived by modelling Disadvantage:  no access to the profile of the cold ion  vibronic structure due to : - the multiphotonic absorption process - the preparation of the ions (ejection process in particular) GASPARIM ANR project:  improve the cooling of the ions (collaboration with S. Schlemmer- Univ. Cologne)  implement a two colour laser scheme (collaboration with T. Pino & Ph. Bréchignac at ISMO-Univ. Paris Sud)

10. The Results – 1-Methylpyrene cation 189 ? 215 ?

11. The Results – 1-Methylpyrene cation

12. Theory Gaussian 09 – B3LYP functionals for geometry optimization and frequency calculations. – BLYP functionals for vertical excited state calculations. – 6-31G(d,p) basis set was chosen after comparing computational cost and accuracy on pyrene cation.

13. Breakdown Pathway -H http://www.chem.uic.edu

14. Spectroscopy of 1-Methylpyrene cation

15. Improved cooling

16. Spectroscopy of 1-Methylpyrene cation Tan, X., Salama, F. (2006), Chem. Phys. Letters., 422, 518-521

17. Spectroscopy of 1-Methylpyrene cation Transition Energy of transition Wavelength (nm) (TD-DFT) (Experiment) Oscillator strength D 4 ← D 0 2.4902 eV 20084.8 (497.89) - 0.0185 D 5 ← D 0 2.8807 eV23234.2 (430.40) 22520 (444) (441 CRD) 0.2339

18. The Results – CH 2 - C 16 H 9 + cation 2 possible structures. The seven member ring system has a calculated S 1 state at 455.11 f=0.1149

19. Breakdown Pathway -H http://www.chem.uic.edu

20. The Results – CH 2 - C 16 H 9 + cation 2 possible structures. The seven member ring system has a calculated S 1 state at 455.11 f=0.1149

21. The Results – CH 2 - C 16 H 9 + cation Transition Energy of transition Wavelength (nm) (TD-DFT) (Experiment) Oscillator strength S 1 ← S 0 2.2230 eV 17929.9 (577.73) -f=0.0608 S 2 ← S 0 2.5120 eV 20260.6 (493.57) 19685 (508 nm) f=0.1241 S 3 ← S 0 2.9193 eV 23545.5 (424.71) ??f =0.1520

22. m/z=189 Calculated electronic properties. Singlet ground state. 5 member ring IR spectrum to confirm. Ring mode at calculated 1713cm -1 (~1670cm -1 ), which is not present in system with just 6 member rings. 548nm0.0125 406nm0.1152 317nm0.0818 255nm0.31

23. The Future 2 laser experiment. Preliminary experiments underway. OPO to probe the spectroscopy with the second laser to break. 2 laser ablation scheme for better control of the ablation – ionization process ~30% Dissociation OPO + 355nm

24. The Future 215.1 214.1 213.1 185.1 187.1 189.1 190.1 161.1 159.1 135.0 134.0 111.0 110.0 109.0 87.0 86.0 85.0 63.0 62.0 61.0 39.0 C3H3+C3H3+ C5H3+C5H3+

25. Acknowledgements Loic Nogues $$$$$: French Nationale de la Recherche (ANR), under grant “Gas- phase PAH research for the interstellar medium.” (GASPARIM) CNRS / Programme National Physique et Chimie du Milieu Interstellaire University Paul Sabatier and Observatory Midi-Pyrénées (AST Molecules and Grains: from laboratory to the universe) Super-Computing Center of Midi-Pyrenees (http://www.calmip.cict.fr)