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Infrared spectra of protonated and hydrogenated corannulene (C20H10) and sumanene (C21H12) using matrix isolation in solid para-hydrogen – implications for the UIR bands

Published online by Cambridge University Press:  12 October 2020

Pavithraa Sundararajan
Affiliation:
Department of Applied Chemistry and Institute of Molecular Science, National Chiao Tung University, Hsinchu30010, Taiwan email: pavi.nctu@gmail.com
Masashi Tsuge
Affiliation:
Institute of Low Temperature Science, Hokkaido University, Sapporo060-0819, Japan email: tsuge@lowtem.hokudai.ac.jp
Masaaki Baba
Affiliation:
Division of Chemistry, Graduate School of Science, Kyoto University, Kyoto606-8502, Japan email: baba.masaaki.3n@kyoto-u.ac.jp
Hidehiro Sakurai
Affiliation:
Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Osaka565-0871, Japan email: hsakurai@chem.eng.osaka-u.ac.jp
Yuan-Pern Lee
Affiliation:
Center for Emergent Functional Matter Science, National Chiao Tung University, Hsinchu 30010, Taiwan and Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei10617, Taiwan email: yplee@mail.nctu.edu.tw
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Abstract

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Polycyclic aromatic hydrocarbons (PAH) and their derivatives, including protonated and cationic species, are suspected to be carriers of the unidentified infrared (UIR) emission bands observed from the galactic and extragalactic sources. We investigated the infrared (IR) spectra of protonated nonplanar PAHs: corannulene (C20H10) and sumanene (C21H12), that are regarded as a fragments of a fullerene,C60. The protonated corannulene H+ C20H10 and sumanene H+ C21H12 were produced in seperate experiments by bombarding a mixture of corannulene/sumanene and para-hydrogen (p-H2) with electrons during deposition at 3.2 K. During maintenance of the electron-bombarded matrix in darkness the intensities of IR lines of protonated corannulene decreased because of neutralization by electrons that were slowly released from the trapped sites whereas the hydrogenated species were produced. The observed lines were classified into several groups according to their responses to darkness and secondary irradiation at 365 nm/385 nm LEDs. Spectral assignments were derived based on a comparison of the observed spectra with those predicted with the B3PW91/6-311+ +G(2d,2p) method. The observed IR spectrum of hub-H+ C20H10, the most stable protonated isomer, resembles several bands of the Class-A UIR bands.

Type
Contributed Papers
Copyright
© International Astronomical Union 2020

References

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