Photodepletion Spectroscopy Of Io^− Within The Actinic Range

McKinnon, Benjamin

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https://hdl.handle.net/2142/111278 Copy

Description

Title

Photodepletion Spectroscopy Of Io⁻ Within The Actinic Range

Author(s)

McKinnon, Benjamin

Contributor(s)

• Trevitt, Adam J.
• Bieske, Evan
• Blanksby, Stephen J.
• Poad, Berwyck
• Ucur, Boris
• Marlton, Samuel

Issue Date

2021-06-24

Keyword(s)

Action spectroscopy (incl. PE, PD, PI, LIR)

Abstract

Iodine oxides (I$_{x}$O$_{y}$) are atmospherically important due to their high reactivity with ozone. The I$^{-}$ anion has been detected in the atmosphere, along with IO$_{2}$$^{-}$ and IO$_{3}$$^{-}$ however, IO$^{-}$ is yet to be directly detected despite being a key intermediate to their formation.\footnote{Frege C. et al., Atmospheric Chemistry and Physics, 2017 / Koenig T. K. et al., Proceedings of the National Academy of Sciences, 2020 / He X.-C. et al., Science, 2021} A recent gas phase study\footnote{Bhujel M. et al., Physical Chemistry and Chemical Physics, 2020} confirms I$^{-}$ will react with ozone to form IO$^{-}$ with subsequent step-wise ozone reactions to form IO$_{2}$$^{-}$ then IO$_{3}$$^{-}$. The aim of the present study is to investigate the photodepletion of IO$^{-}$ within the visible range of 650 - 450 nm (15385 - 22222 $\wn$) ${via}$ photodetachment and photodissociation spectroscopy. Gas phase spectra are obtained at room temperature by coupling a tuneable OPO laser with a linear ion-trap mass spectrometer. A bound excited state is present in this visible range, which will either undergo autodetachment ${via}$ electron loss (IO$^{\bullet}$ + e$^{-}$) or undergo photodissociation (I$^{-}$ + O($^{3}$P)). Depending on the vibrational energy level of the excited state, either photodissociation or photodetachment is favoured. Investigation of the potential energy surface using the multireference configuration interaction (MRCI) method shows that within the investigated energy range IO$^{-}$ will excite from the $X^{1}\Sigma^{+}$ ground state and populate the 1$^{1}\Pi$ excited state and, in the Franck-Condon region, this is close to the curve crossing that mediates the photodissociation and close to the electron affinity for electron detachment. From this study IO$^{-}$ has been shown to photodeplete at visible wavelengths and, with previous studies showing that IO$^{-}$ will react with ozone to form higher order iodine oxides, may together contribute to the low abundance of IO$^{-}$ in the atmosphere and therefore why it has eluded detection.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

Text

Language

eng

Permalink

http://hdl.handle.net/2142/111278

DOI

10.15278/isms.2021.RM05

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