Infrared Spectra of Protonated Pyrene and Its Neutral Counterpart in Solid para-Hydrogen.
Protonated polycyclic aromatic hydrocarbons (H(+)PAHs) have been reported to have infrared (IR) bands at wavenumbers near those of unidentified infrared (UIR) emission bands from interstellar objects. We produced 1-C16H11(+) and 1-C16H11 upon electron bombardment during matrix deposition of p-H2 containing pyrene (C16H10) in a small proportion. Intensities of absorption features of 1-C16H11(+) decreased after the matrix was maintained in darkness or irradiated with light at 365 nm, whereas those of 1-C16H11 increased. The observed line wavenumbers and relative intensities of 1-C16H11(+) and 1-C16H11 agree satisfactorily with the scaled vibrational wavenumbers and IR intensities predicted with the B3PW91/6-311++G(2d,2p) method. Our method, being relatively clean with negligible fragmentation, is applicable to larger H(+)PAH; it has the advantages of producing excellent IR spectra covering a broad spectral range with narrow lines and accurate intensities, so that structural identification among various isomers is feasible.
†Department of Applied Chemistry and Institute of Molecular Science, National Chiao Tung University, 1001 Ta-Hsueh Road, Hsinchu 30010, Taiwan.
Mohammed
M
Bahou
‡National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu 30076, Taiwan.
Yu-Jong
YJ
Wu
†Department of Applied Chemistry and Institute of Molecular Science, National Chiao Tung University, 1001 Ta-Hsueh Road, Hsinchu 30010, Taiwan.|§Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan.
Yuan-Pern
YP
Lee
C16H11; C16H11+; IR spectroscopy; matrix isolation; p-H2; pyrene