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Protonated Pyrene (1-C16H11+) and Its Neutral Counterpart (1-C16H11)

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Presentation on theme: "Protonated Pyrene (1-C16H11+) and Its Neutral Counterpart (1-C16H11)"— Presentation transcript:

1 Protonated Pyrene (1-C16H11+) and Its Neutral Counterpart (1-C16H11)
Identification of Protonated Pyrene (1-C16H11+) and Its Neutral Counterpart (1-C16H11) Isolated in Solid Para-Hydrogen Mohammed Bahou, Yu-Jong Wu, Yuan-Pern Lee Dept. Applied Chemistry & Inst. Molecular Science National Chiao Tung University, Taiwan

2 Outline Importance of protonated PAH (H+PAH)
Previous methods in studying IR of H+PAH Ion trap + IRMPD Ar-tagging + IR photodissociation Advantages of using p-H2 Making protonated species with an e-gun IR spectra of H+benzene & H+naphthalene IR spectra of H+Pyrene & H+Coronene

3 Unidentified Infrared (UIR) Emission
Orion bar Unit: mm 3.3 : aromatic C-H stretch 6.2, 7.7 : aromatic CC stretch 8.6: ring bend 11.3, 13.5, 16.4: deformation

4 Possible Sources of UIR Bands
PAH N-PAH PAH N-PAH+ H+PAH HnPAH UV e- H+ IR emission ApJ 678, 316 (2008) Science 265, 1686 (1994) J. Phys. Chem. 99, 8978 (1995) PAH (Polycyclic Aromatic Hydrocarbons) Nature 391, 259 (1998)

5 Protonated PAH (H+PAH)
Closed-shell electronic configuration No entrance barrier for protonation to PAH Large abundance of proton sources in space No further reaction of H+PAH with H or H2

6 Spectrosocpy of Protonated PAH

7 IRMPD of Protonated Naphthalene
Angew. Chem. Int. Ed. 46, 6714 (2007) Ion cyclotron resonance (ICR) ion trap Free electron laser (FEL) IR multiphoton dissociation (IRMPD) Dopfer et al., Ap. J. Lett. 706, L66 (2009)

8 Ar-Tagging / IR Dissociation
h (IR) …….it agrees better with the patterns for the α isomer, which is the expected lower-energy species, although some contribution from the β isomer cannot be ruled out Duncan et al., Ap. J. 702, 301 (2009)

9 Experimental Setup H3+ + PAH  H+PAH + H2 H + PAH  HPAH
KBr KBr window Light from FT-IR MCT detector UV/Vis light E-gun: e- (250 eV, 3070 mA) Sample inlet Quartz PAH/p-H2 (1/10001/3000) Cryostat (3 K) H3+ + PAH  H+PAH + H2 H + PAH  HPAH H+PAH + e  HPAH

10 Advantages of p-H2 as a Matrix Host
Quantum solid- large amplitude of ZP vibration High resolution Rotation Diminished cage effect Nuclear spin relaxation softness

11 Production of Radicals in p-H2
Photolysis in situ CH3SSCH3  CH3S CH3OSOCl  CH3OSO J. Chem. Phys. 133, (2010) J. Chem. Phys. 136, (2012) B. Bimolecular Reactions J. Phys. Chem. Lett. 1, 2956 (2010) CH3 + SO2  CH3SO2 J. Chem. Phys. 134, (2011)

12 Comparison of C6H7+ Spectra
W. Jones et al., Angew. Chem. Int. Ed. 42, 2057 (2003) Douberly et al. J. P. C. A 112, 4869 (2008) J. Chem. Phys. 136, (2012)

13 Comparison of 1-C10H9+ Phys. Chem. Chem. Phys., 15, 1907 (2013)

14 Comparison of 2-C10H9+

15 Comparison of IR spectra of C10H9
Phys. Chem. Chem. Phys., 15, 1907 (2013)

16 Pyrene (C16H10) Experiments
J. Phys. Chem. Lett. 4, 1989 (2013) Deposit (1/1500) 365 nm 2.5 hr Darkness 20 h

17 Protonated Pyrene (C16H11+)

18

19 Hydrogenated Pyrene (C16H11)

20

21 Comparison of UIR with C16H11+ & C16H11
6.2 7.8 8.6 11.2 3.3 7.6

22 Summary 1-C16H11+ and 1-C16H11 were produced upon electron-impact during deposition of a mixture of C16H10/p-H2. Visible light or keeping for a prolonged period converts 1-C16H11+ to 1-C16H11. This method is superior to others in making protonated PAH and its neutrals Clean and easy– nearly no fragmentation Narrow width– identification of isomers Wide spectral coverage

23 Comparison of H+Coronene (C24H13+)
B3PW91/6311++g(2d,2p) 0.978 Experiments

24 Comparison of H+Coronene with UIR

25 Acknowledgments Yu-Jong Wu NSRRC Matrix: Momo Bahou, Yu-Jong Wu

26 Building Blocks of PAH Hudgins & Allamandola, J. Phys. Chem. 99, 3033 (1995)

27 Protonated Naphthalene (C10H9+)
4a-C10H9+ a-C10H9 + b-C10H9+ 4a

28 Vibrational Wavenumbers
anharmonic. -C10H9+ anharmonic -C10H9+ 1- C10H9+ IRPD Duncan 2- C10H9 1625 (37) 1625 (100) 1618.7 1617 1623.9 1487.3 1473.4 1571 (28) 1610 (11) 1580.8 1575 1608.8 1446.0 1432.2 1516 (100) 1507 (13) 1510.0 1506 1505.4 1403.9 1385.1 1459 (53) 1471 (49) 1457.9 1454/1480 1472.0 942.3 1332.6 1421 (13) 1400 (43) 1421.7 1418 1399.1 778.1 906.1 1366 (34) 1333 (13) 1361.7 1358/1378/1391 1325.9 648.5 893.1 1291 (46) 1287 (22) 1292.4 1295 771.4 1242 (10) 1267 (56) 1242.1 1236/1271/1252 1265.6 1171 (13) 1162.7 1164 920.5 747.1 B3PW91/6311++g(2d,2p).


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