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Title: Photodissociation of CO{sub 2}{sup -} in water clusters via Renner-Teller and conical interactions

Abstract

The photochemistry of mass selected CO{sub 2}{sup -}(H{sub 2}O){sub m}, m=2-40 cluster anions is investigated using 266 nm photofragment spectroscopy and theoretical calculations. Similar to the previous 355 nm experiment [Habteyes et al., Chem. Phys. Lett. 424, 268 (2006)], the fragmentation at 266 nm yields two types of anionic products: O{sup -}(H{sub 2}O){sub m-k} (core-dissociation products) and CO{sub 2}{sup -}(H{sub 2}O){sub m-k} (solvent-evaporation products). Despite the same product types, different electronic transitions and dissociation mechanisms are implicated at 355 and 266 nm. The 355 nm dissociation is initiated by excitation to the first excited electronic state of the CO{sub 2}{sup -} cluster core, the 1 {sup 2}B{sub 1}({sup 2}A{sup ''}) state, and proceeds via a glancing Renner-Teller intersection with the ground electronic state at a linear geometry. The 266 nm dissociation involves the second excited electronic state of CO{sub 2}{sup -}, the 2 {sup 2}A{sub 1}({sup 2}A{sup '}) state, which exhibits a conical intersection with the 3 {sup 2}B{sub 2}(A{sup '}) state at a bent geometry. The asymptotic O{sup -} based products are believed to be formed via this 3 {sup 2}B{sub 2}(A{sup '}) state. By analyzing the fragmentation results, the bond dissociation energy of CO{sub 2}{sup -} to O{supmore » -}+CO in hydrated clusters (m{>=}20) is estimated as 2.49 eV, compared to 3.46 eV for bare CO{sub 2}{sup -}. The enthalpy of evaporation of one water molecule from asymptotically large CO{sub 2}{sup -}(H{sub 2}O){sub m} clusters is determined to be 0.466{+-}0.001 eV (45.0{+-}0.1 kJ/mol). This result compares very favorably with the heat of evaporation of bulk water, 0.456 eV (43.98 kJ/mol)« less

Authors:
; ;  [1]
  1. Department of Chemistry, University of Arizona, 1306 E. University Boulevard, Tucson, Arizona 85721-0041 (United States)
Publication Date:
OSTI Identifier:
20991246
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 126; Journal Issue: 15; Other Information: DOI: 10.1063/1.2717932; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; CARBON COMPOUNDS; DISSOCIATION; DISSOCIATION ENERGY; ENTHALPY; EV RANGE 01-10; EVAPORATION; EXCITED STATES; FRAGMENTATION; MOLECULAR CLUSTERS; OXYGEN IONS; PHOTOCHEMISTRY; PHOTOLYSIS; WATER

Citation Formats

Habteyes, Terefe, Velarde, Luis, and Sanov, Andrei. Photodissociation of CO{sub 2}{sup -} in water clusters via Renner-Teller and conical interactions. United States: N. p., 2007. Web. doi:10.1063/1.2717932.
Habteyes, Terefe, Velarde, Luis, & Sanov, Andrei. Photodissociation of CO{sub 2}{sup -} in water clusters via Renner-Teller and conical interactions. United States. doi:10.1063/1.2717932.
Habteyes, Terefe, Velarde, Luis, and Sanov, Andrei. Sat . "Photodissociation of CO{sub 2}{sup -} in water clusters via Renner-Teller and conical interactions". United States. doi:10.1063/1.2717932.
@article{osti_20991246,
title = {Photodissociation of CO{sub 2}{sup -} in water clusters via Renner-Teller and conical interactions},
author = {Habteyes, Terefe and Velarde, Luis and Sanov, Andrei},
abstractNote = {The photochemistry of mass selected CO{sub 2}{sup -}(H{sub 2}O){sub m}, m=2-40 cluster anions is investigated using 266 nm photofragment spectroscopy and theoretical calculations. Similar to the previous 355 nm experiment [Habteyes et al., Chem. Phys. Lett. 424, 268 (2006)], the fragmentation at 266 nm yields two types of anionic products: O{sup -}(H{sub 2}O){sub m-k} (core-dissociation products) and CO{sub 2}{sup -}(H{sub 2}O){sub m-k} (solvent-evaporation products). Despite the same product types, different electronic transitions and dissociation mechanisms are implicated at 355 and 266 nm. The 355 nm dissociation is initiated by excitation to the first excited electronic state of the CO{sub 2}{sup -} cluster core, the 1 {sup 2}B{sub 1}({sup 2}A{sup ''}) state, and proceeds via a glancing Renner-Teller intersection with the ground electronic state at a linear geometry. The 266 nm dissociation involves the second excited electronic state of CO{sub 2}{sup -}, the 2 {sup 2}A{sub 1}({sup 2}A{sup '}) state, which exhibits a conical intersection with the 3 {sup 2}B{sub 2}(A{sup '}) state at a bent geometry. The asymptotic O{sup -} based products are believed to be formed via this 3 {sup 2}B{sub 2}(A{sup '}) state. By analyzing the fragmentation results, the bond dissociation energy of CO{sub 2}{sup -} to O{sup -}+CO in hydrated clusters (m{>=}20) is estimated as 2.49 eV, compared to 3.46 eV for bare CO{sub 2}{sup -}. The enthalpy of evaporation of one water molecule from asymptotically large CO{sub 2}{sup -}(H{sub 2}O){sub m} clusters is determined to be 0.466{+-}0.001 eV (45.0{+-}0.1 kJ/mol). This result compares very favorably with the heat of evaporation of bulk water, 0.456 eV (43.98 kJ/mol)},
doi = {10.1063/1.2717932},
journal = {Journal of Chemical Physics},
number = 15,
volume = 126,
place = {United States},
year = {Sat Apr 21 00:00:00 EDT 2007},
month = {Sat Apr 21 00:00:00 EDT 2007}
}
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