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Current models for the optically prepared 2 A2 potential energy surface along the asymmetric stretch coordinate: (A) Potential energy surface determined by analysis of the gas-phase absorption spectrum; 7 (B) potential energy surface determined by ab initio theoretical analysis; 56-58 (C) potential energy surface determined by resonance Raman intensity analysis of OClO in water and cyclohexane . 28,32
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The photochemical reaction dynamics of chlorine dioxide (OClO) are investigated using absorption and resonance Raman spectroscopy. The first Raman spectra of gaseous OClO obtained directly on resonance with the B-2(1)-(2)A(2) electronic transition are reported. Significant scattering intensity is observed for all vibrational degrees of freedom (the...
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Citations
... Note that the specific Raman peak of chlorine dioxide at 944 cm −1 in Figure 1 is consistent with previously published data. 27 Although the peak rapidly decreased in intensity during the measurement, it disappeared in approximately 15 minutes indicating that chlorine dioxide disappeared from the solution, either by chemical decomposition into chlorine or by diffusing out. Taken all together, we conclude that spores inactivated by treatment with chlorine dioxide did not show any major changes in neither their Raman spectra as measure by LTRS, or exosporium and spore coat, as visualize using SEM, or internally as visualized using TEM. ...
Contamination of toxic spore-forming bacteria is problematic since spores can survive a plethora of disinfection chemicals. It is also problematic to rapidly detect if the disinfection chemical was active, leaving spores dead. Robust decontamination strategies, as well as reliable detection methods to identify dead from viable spores, are thus critical. Vibrational detection methods such as Raman spectroscopy has been suggested for rapid diagnostics and differentiation of live and dead spores. We investigate in this work, using laser tweezers Raman spectroscopy, the changes in Raman spectra of Bacillus thuringiensis spores treated with sporicidal agents such as chlorine dioxide, peracetic acid, and sodium hypochlorite. We also imaged treated spores using SEM and TEM to verify if any changes to the spore structure can be correlated to the Raman spectra. We found that chlorine dioxide did not change the Raman spectrum or the spore structure; peracetic acid shows a time-dependent decrease in the characteristic DNA/DPA peaks and 20 % of the spores were degraded and collapsed; spores treated with sodium hypochlorite show an abrupt drop in DNA and DPA peaks within 20 minutes all though the spore structure was overall intact, however, the exosporium layer was reduced. Structural changes appeared over several minutes, compared to the inactivation time of the spores, which is less than a minute. We conclude that vibrational spectroscopy provides powerful means to detect changes in spores but it might be problematic to identify if spores are live or dead after a decontamination procedure.
... A peak for chlorine dioxide gas is observed at 360 nm with distinctive vibrational fine structure (see Figure 2). This electronic spectrum is discussed in detail elsewhere (see Esposito, 1999). It may be helpful to take a scan of chlorine gas to compare it to the chlorine dioxide spectrum. ...
After performing this experiment, the student shall be able to:
Produce a relatively uncommon, environmentally friendly, oxidizing and disinfecting gas.
Visualize an application of Frost diagrams.
Perform a disproportionation reaction.
Produce the same substance by different paths (i.e., oxidation, reduction and disproportionation).
... Therefore, the presence of transitions having asymmetric-stretch overtone character demonstrates that the ground and excited potential energy surfaces are substantially different along this coordinate. This conclusion has been confirmed by resonance Raman scattering studies of gaseous OClO (53). When aCl is compared using excitation that is resonant with transitions involving the symmetric-stretch coordinate exclusively, versus wavelengths resonant with transitions involving the asymmetric-stretch coordinate as well, a,-, is significantly reduced when transitions involving the asymmetric stretch are excited (17). ...
... The most interesting feature of this spectrum is modest intensity at 2190 cm-' corresponding to the asymmetric-stretch overtone transition (Fig. 3, middle). This same transition demonstrates substantial intensity in the resonance Raman spectrum of gaseous OC10; therefore, this intensity difference suggests that the evolution along the asymmetric stretch is significantly altered in solution (53). RRIA studies have also been performed on OClO dissolved in water and chloroform and essentially no intensity was observed for the asymmetric-stretch overtone transition consistent with the absence of structural evolution along this coordinate (67,68). ...
Recent progress in understanding the phase-dependent reactivity of halooxides and nitrosyl halides is outlined. Halooxide reactivity is represented by the photochemistry of chlorine dioxide (OClO) and dichlorine monoxide (ClOCl). The gas phase photochemical dynamics of OClO are contrasted with the dynamics in condensed environments. The role of excited-state symmetry in defining the reaction dynamics and the observation of photoisomerization resulting in the production of ClOO are discussed. The current understanding of the excited-state reaction dynamics of ClOCl and evidence for photoisomerization of this species resulting in the production of ClClO are outlined. Finally, the photochemical reaction dynamics of the nitrosyl halide ClNO are presented. The main difference between the gas and condensed phase reaction dynamics of this species is that whereas photodissociation to form Cl and NO dominates the gas phase reaction dynamics, photoisomerization resulting in ClON production occurs to an appreciable extent in condensed environments. The observation of photoisomerization for OClO, ClOCl and ClNO suggests that this process is a general feature of the condensed phase reaction dynamics for smaller halooxides and nitrosyl halides. Finally, future areas for study in both halooxide and nitrosyl halide photoreactivity are outlined.
... The role of solvent in the excited-state reaction dynamics of OClO has been explored using absolute resonance Raman intensity analysis ͑RRIA͒. [15][16][17][18] These studies have demonstrated that structural evolution along the asymmetric-stretch coordinate is restricted in solution result-ing in the preservation of ground-state C 2v symmetry in the excited state. The preservation of C 2v symmetry is a primary factor for the enhanced Cl production in condensed environments. ...
The solvation dynamics following photoexcitation of chlorine dioxide OClO in different solvents are investigated by classical molecular dynamics. Following previous work on the aqueous response to OClO photoexcitation J. Chem. Phys. 118, 4563 2003, the present study considers the response of chloroform and cyclohexane; these three liquids present unique solvent environments that differ significantly in both polarity and structure. The study is designed to ascertain the origin of the solvent-invariant homogeneous linewidth associated with OClO photoexcitation and to confirm, at the molecular level, whether the relaxation dynamics are similar across dissimilar solvents due to chance or a common relaxation origin. The results obtained here are used to predict the time scale of solvent-induced optical dephasing, and excellent agreement with experiment is observed for all solvents. Analysis demonstrates that the solvation dynamics of OClO are dominated by short-ranged mechanical solute–solvent interactions regardless of the identity and electrostatic properties of the solvent. Low-frequency translational motions dominate the coupling spectrum, and virtually no contribution to energy gap relaxation is achieved through intramolecular solvent motions. The invariant homogeneous linewidth is attributed to the similarity in the primary response of all solvents to OClO photoexcitation. © 2003 American Institute of Physics.
Progress in understanding the phase-dependent reactivity of chlorine dioxide (OClO) is outlined. Resonance Raman intensity analysis studies of gaseous and solution-phase OClO are presented which demonstrate that the optically prepared excited state undergoes significant modification in solution. In addition, time- resolved resonance Raman studies are presented which demon- strate that geminate recombination of the primary photoproducts, resulting in the re-formation of ground-state OClO, dominates the photochemical reaction dynamics in solution. The current picture of aqueous OClO photochemistry derived from these studies is discussed, and future directions of investigation are outlined.
Progress in understanding the phase-dependent reactivity of chlorine dioxide (OClO) is outlined. Resonance Raman intensity analysis studies of gaseous and solution-phase OClO are presented which demonstrate that the optically prepared excited state undergoes significant modification in solution. In addition, time-resolved resonance Raman studies are presented which demonstrate that geminate recombination of the primary photoproducts, resulting in the re-formation of ground-state OClO, dominates the photochemical reaction dynamics in solution. The current picture of aqueous OClO photochemistry derived from these studies is discussed, and future directions of investigation are outlined.
