“…Although the absorption spectrum of OClO in cyclohexane is more diffuse than the gas-phase spectrum, it should be noted that the structured spectrum in cyclohexane stands in contrast to the relatively unstructured spectrum observed in water demonstrating that the observed broadening is solvent dependent (see below) . The maximum absorption cross section for OClO in cyclohexane is 0.042 Å 2 , very close to the value determined for OClO in water and that determined from electron-energy-loss spectroscopy. , 1 Experimental (solid) and calculated (dashed) electronic absorption spectra of chlorine dioxide (OClO) in cyclohexane. Calculated spectra are from analysis employing (A) Gaussian homogeneous broadening and a harmonic model of the excited-state potential energy surface, (B) Lorentzian homogeneous broadening and an anharmonic model of the excited-state potential energy surface, and (C) Gaussian homogeneous broadening and an anharmonic model of the excited-state potential energy surface.…”
Resonance Raman spectra of chlorine dioxide (OClO) dissolved in cyclohexane obtained with excitation throughout the 2 B 1 -2 A 2 electronic transition are presented. Resonance Raman intensity corresponding to all vibrational degrees of freedom (the symmetric stretch, bend, and asymmetric stretch) is observed, demonstrating that excited-state structural evolution along all three coordinates occurs upon photoexcitation. The electronic absorption and absolute resonance Raman cross sections are reproduced employing the time-dependent formalism for Raman scattering using an anharmonic description of the 2 A 2 , excited-state potential-energy surface. Analysis of the resonance Raman cross-sections demonstrates that both homogeneous and inhomogeneous broadening mechanisms are operative in cyclohexane. Comparison of the experimentally determined, gas-phase 2 A 2 surface to that in solution defined by the analysis presented here shows that although displacements along the symmetric stretch and bend are similar in both phases, evolution along the asymmetric stretch is dramatically altered in solution. Specifically, employing the gas-phase potential along this coordinate, the predicted intensity of the overtone transition is an order of magnitude larger than that observed. The analysis presented here demonstrates that the asymmetric stretch overtone intensity is consistent with a reduction in excited-state frequency along this coordinate from 1100 to 750 ( 100 cm -1 . This comparison suggests that differences in evolution along the asymmetric stretch may be responsible for the phase-dependent reactivity of OClO. In particular, the absence of substantial evolution along the asymmetric stretch in solution results in the ground-state symmetry of OClO being maintained in the 2 A 2 excited state. The role of symmetry in defining the reaction coordinate and the nature of the solvent interaction responsible for modulation of the excited-state potential energy surface are discussed.
“…Although the absorption spectrum of OClO in cyclohexane is more diffuse than the gas-phase spectrum, it should be noted that the structured spectrum in cyclohexane stands in contrast to the relatively unstructured spectrum observed in water demonstrating that the observed broadening is solvent dependent (see below) . The maximum absorption cross section for OClO in cyclohexane is 0.042 Å 2 , very close to the value determined for OClO in water and that determined from electron-energy-loss spectroscopy. , 1 Experimental (solid) and calculated (dashed) electronic absorption spectra of chlorine dioxide (OClO) in cyclohexane. Calculated spectra are from analysis employing (A) Gaussian homogeneous broadening and a harmonic model of the excited-state potential energy surface, (B) Lorentzian homogeneous broadening and an anharmonic model of the excited-state potential energy surface, and (C) Gaussian homogeneous broadening and an anharmonic model of the excited-state potential energy surface.…”
Resonance Raman spectra of chlorine dioxide (OClO) dissolved in cyclohexane obtained with excitation throughout the 2 B 1 -2 A 2 electronic transition are presented. Resonance Raman intensity corresponding to all vibrational degrees of freedom (the symmetric stretch, bend, and asymmetric stretch) is observed, demonstrating that excited-state structural evolution along all three coordinates occurs upon photoexcitation. The electronic absorption and absolute resonance Raman cross sections are reproduced employing the time-dependent formalism for Raman scattering using an anharmonic description of the 2 A 2 , excited-state potential-energy surface. Analysis of the resonance Raman cross-sections demonstrates that both homogeneous and inhomogeneous broadening mechanisms are operative in cyclohexane. Comparison of the experimentally determined, gas-phase 2 A 2 surface to that in solution defined by the analysis presented here shows that although displacements along the symmetric stretch and bend are similar in both phases, evolution along the asymmetric stretch is dramatically altered in solution. Specifically, employing the gas-phase potential along this coordinate, the predicted intensity of the overtone transition is an order of magnitude larger than that observed. The analysis presented here demonstrates that the asymmetric stretch overtone intensity is consistent with a reduction in excited-state frequency along this coordinate from 1100 to 750 ( 100 cm -1 . This comparison suggests that differences in evolution along the asymmetric stretch may be responsible for the phase-dependent reactivity of OClO. In particular, the absence of substantial evolution along the asymmetric stretch in solution results in the ground-state symmetry of OClO being maintained in the 2 A 2 excited state. The role of symmetry in defining the reaction coordinate and the nature of the solvent interaction responsible for modulation of the excited-state potential energy surface are discussed.
“…As Figure illustrates, this model is capable of reproducing the observed vibrational progressions and overall intensity of the absorption spectrum. The absorption cross sections at higher frequencies are underestimated; however, other transitions located further in the UV and/or the presence of a weak transition to the 2 A 1 state may contribute to the absorption intensity in this region. ,, In particular, the resonance Raman depolarization ratios are less than 0.33 (Table ), an observation that is consistent with the participation of a second excited state in the scattering process (see above). ,, …”
Resonance Raman spectra of aqueous chlorine dioxide (OClO) are
measured for several excitation wavelengths
spanning the photochemically relevant
2B1−2A2 optical
transition. A mode-specific description of the
optically
prepared, 2A2 potential energy surface is
derived by simultaneous analysis of the absolute resonance
Raman
and absorption cross sections. The resonance Raman spectra are
dominated by transitions involving the
symmetric stretch and bend coordinates demonstrating that excited-state
structural evolution occurs
predominately along these degrees of freedom. Scattering intensity
is not observed for transitions involving
the asymmetric stretch, demonstrating that excited-state structural
evolution along this coordinate is modest.
The limited evolution along the asymmetric stretch coordinate
results in the preservation of
C
2
v
symmetry
on
the 2A2 surface. It is proposed that this
preservation of symmetry is responsible for the increase in
Cl
photoproduct quantum yield in solution relative to the gas phase.
Analysis of the absolute scattering cross
sections also demonstrates that the homogeneous line width for the
2B1−2A2 optical
transition in water is
essentially identical to that in cyclohexane; however, the extent of
inhomogeneous broadening increases
dramatically in aqueous solution. Comparison of the spectroscopic
properties of OClO to the properties of
isoelectronic O3
- is made to elucidate the
origin of the solvent response to OClO photoexcitation. It
is
suggested that solvent−solute dipole−dipole coupling and
intermolecular hydrogen bonding represent the
largest components of the solvent coordinate.
“…The Rydberg series of OClO radical had experimentally been assigned by several authors 1,13,14 in 1990s and there has been controversy about some bands assignment. In the present work, we also carried out the calculations related to these Rydberg states at the MS-CASPT2 level, and the detailed assignments were made.…”
Section: Introductionmentioning
confidence: 99%
“…Furthermore, the absorption cross sections 5,[13][14][15] and infrared absorption spectra of the OClO isomer in inert matrix 6 and gas phase 7,8 have been extensively studied. In contrast to the intense interest, both experimental and theoretical, in the neutral chlorine dioxide, the ions of this species, OClO + and OClO À , have received relatively little attention.…”
Using the complete active space self-consistent field method with a large atomic natural orbital basis set, 10, 13, and 9 electronic states of the OClO radical, OClO(+) cation, and OClO(-) anion were calculated, respectively. Taking the further correlation effects into account, the second-order perturbation (CASPT2) calculations were carried out for the energetic calibration. The photoelectron spectroscopy of the OClO radical and OClO(-) anion were extensively studied in the both case of the adiabatic and vertical ionization energies. The calculated results presented the relatively complete assignment of the photoelectron bands of the experiments for OClO and its anion. Furthermore, the Rydberg states of the OClO radical were investigated by using multiconfigurational CASPT2 (MS-CASPT2) theory under the basis set of large atomic natural orbital functions augmented with an adapted 1s1p1d Rydberg functions that have specially been built for this study. Sixteen Rydberg states were obtained and the results were consistent with the experimental results.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
