Isomerization and dehydrogenation of highly vibrationally excited azulene+ produced via S2 vibrational manifold

• Published in: Chemical physics letters Vol. 745; p. 137250
• Main Authors: Vinitha, M.V., Nair, Arya M., Kumar, Abhishek S., Blanchet, Valerie, Kadhane, Umesh R.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 16-04-2020; Elsevier
• Subjects: Chemical Physics; Physics
• ISSN: 0009-2614; 1873-4448
• DOI: 10.1016/j.cplett.2020.137250

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•Excited state dynamics of PAHs helps multi step absorption of UV photons.•Cations are produced with very narrow internal energy distribution.•Azulene ionisation with a single ns UV laser is dominated by S2 ionization channel.•It helped to produce azulene cations with very narrow and known IED.
High resolution energy-ToF correlation spectrometer and a nanosecond laser is employed to extract H loss rate in hot azulene cations in UV region. Correlation between the photon wavelength and H-loss rate is obtained for 3-photon process and it is explained by a two-step mechanism: (i) 1 + 1 ionization with ultrafast internal conversion to the long-lived S2 state (ii) the increase of internal energy by absorption of the third photon and isomerization. The work uncovers the role of S2 state dynamics in Azulene in controlling the internal energy to a very narrow range.