Communication: Photodissociation of N2O—Frustrated NN bond breaking causes diffuse vibrational structures

Schinke, Reinhard; Suárez, Jaime; Farantos, Stavros C.

doi:10.1063/1.3479391

Cited by 29 publications

(35 citation statements)

References 19 publications

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“…13; a similar deviation was observed for N 2 O. 41,42 The overall agreement with the measured cross section is good. The FWHM of the calculated cross section is about 10% smaller than for the experimental cross section.…”

Section: B State-resolved Cross Sectionssupporting

confidence: 71%

“…We have studied the photodissociation of N 2 O in a series of papers and essentially all experimental results have been well reproduced. [41][42][43][44][45][46][47][48][49] A consistent and nearly complete picture has thus been obtained. This paper is part of a similar investigation of the UV photodissociation of OCS.…”

Section: Introductionmentioning

confidence: 54%

“…The first recurrence is due to NN stretching and the second one, which leads to the weak vibrational structures, is caused by combined large-amplitude bending and NN stretching motion trapped in the bent potential well. 41,47 Because the A state PES of OCS has a much smaller gradient ∂V A /∂r near the FC region than the N 2 O PES, excitation of the CO bond is very weak throughout the fragmentation and trapping in the well near γ = 48 • is negligible. In other words, the particular motion leading to the recurrences in the N 2 O autocorrelation function is absent in the fragmentation of OCS via the A and B states.…”

Section: A Autocorrelation Functionmentioning

confidence: 99%

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The ultraviolet spectrum of OCS from first principles: Electronic transitions, vibrational structure and temperature dependence

Schmidt

Johnson

McBane

et al. 2012

The Journal of Chemical Physics

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Global three dimensional potential energy surfaces and transition dipole moment functions are calculated for the lowest singlet and triplet states of carbonyl sulfide at the multireference configuration interaction level of theory. The first ultraviolet absorption band is then studied by means of quantum mechanical wave packet propagation. Excitation of the repulsive 2 1 A state gives the main contribution to the cross section. Excitation of the repulsive 1 1 A state is about a factor of 20 weaker at the absorption peak (E ph ≈ 45 000 cm −1 ) but becomes comparable to the 2 1 A state absorption with decreasing energy (35 000 cm −1 ) and eventually exceeds it. Direct excitation of the repulsive triplet states is negligible except at photon energies E ph < 38 000 cm −1 . The main structure observed in the cross section is caused by excitation of the bound 2 3 A state, which is nearly degenerate with the 2 1 A state in the Franck-Condon region. The structure observed in the low energy tail of the spectrum is caused by excitation of quasi-bound bending vibrational states of the 2 1 A and 1 1 A electronic states. The absorption cross sections agree well with experimental data and the temperature dependence of the cross section is well reproduced.

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Section: B State-resolved Cross Sectionssupporting

confidence: 71%

Section: Introductionmentioning

confidence: 54%

Section: A Autocorrelation Functionmentioning

confidence: 99%

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The ultraviolet spectrum of OCS from first principles: Electronic transitions, vibrational structure and temperature dependence

Schmidt

Johnson

McBane

et al. 2012

The Journal of Chemical Physics

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“…Probably due to inaccuracies of the TDMs, the calculated cross section is about 30 % smaller than the measured one and therefore it was multiplied by 1.3 in Fig. 1; a similar deviation was observed for N 2 O (Schinke et al, 2010;Schinke, 2011). Overall, the theoretical and experimental cross sections are in good agreement including the width of the broad continuum and the positions and intensities of the superimposed structures.…”

Section: Isotopic Fractionationsupporting

confidence: 64%

OCS photolytic isotope effects from first principles: sulfur and carbon isotopes, temperature dependence and implications for the stratosphere

et al. 2013

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The isotopic fractionation in OCS photolysis is studied theoretically from first principles. UV absorption cross sections for OCS, OC33S, OC34S, OC36S and O13CS are calculated using the time-depedent quantum mechanical formalism and a recently developed ab-initio description of the photodissociation of OCS which takes into account the lowest four singlet and lowest four triplet electronic states. The calculated isotopic fractionations as a function of wavelength are in good agreement with recent measurements by Hattori et al. (2011) and indicate that photolysis leads to only a small enrichment of 34S in the remaining OCS. The photodissociation dynamics provide strong evidence that the photolysis quantum yield is unity at all wavelengths for atmospheric UV excitation, for all isotopologues. A simple stratospheric model is constructed taking into account the main sink reactions of OCS and it is found that overall stratospheric removal slightly favors light OCS in constrast to the findings of Leung et al. (2002). These results show, based on isotopic considerations, that OCS is an acceptable source of background stratosperic sulfate aerosol in agreement with a recent model study of of Brühl et al. (2012). The 13C isotopic fractionation due to photolysis of OCS in the upper stratosphere is significant and will leave a clear signal in the remaining OCS making it a candidate for tracing using the ACE-FTS and MIPAS data sets

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“…18 For comparison, the structures of the N 2 O UV absorption spectrum reflect strongly mixed bending and N 2 motion in the dissociative A state. 13,32 The cross sections of Fig. 2(b) have to be compared to those in Fig.…”

Section: Absorption Cross Sectionmentioning

confidence: 99%

Ultraviolet photodissociation of OCS: Product energy and angular distributions

McBane

Schmidt

Johnson

et al. 2013

The Journal of Chemical Physics

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The ultraviolet photodissociation of carbonyl sulfide (OCS) was studied using three-dimensional potential energy surfaces and both quantum mechanical dynamics calculations and classical trajectory calculations including surface hopping. The transition dipole moment functions used in an earlier study [J. A. Schmidt, M. S. Johnson, G. C. McBane, and R. Schinke, J. Chem. Phys. 137, 054313 (2012)] were improved with more extensive treatment of excited electronic states. The new functions indicate a much larger contribution from the 1 1 A state ( 1 − in linear OCS) than was found in the previous work. The new transition dipole functions yield absorption spectra that agree with experimental data just as well as the earlier ones. The previously reported potential energy surfaces were also empirically modified in the region far from linearity. The resulting product state distributions P v,j , angular anisotropy parameters β(j), and carbon monoxide rotational alignment parameters A (2) 0 (j ) agree reasonably well with the experimental results, while those computed from the earlier transition dipole and potential energy functions do not. The higher-j peak in the bimodal rotational distribution is shown to arise from nonadiabatic transitions from state 2 1 A to the OCS ground state late in the dissociation.

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Communication: Photodissociation of N2O—Frustrated NN bond breaking causes diffuse vibrational structures

Cited by 29 publications

References 19 publications

The ultraviolet spectrum of OCS from first principles: Electronic transitions, vibrational structure and temperature dependence

The ultraviolet spectrum of OCS from first principles: Electronic transitions, vibrational structure and temperature dependence

OCS photolytic isotope effects from first principles: sulfur and carbon isotopes, temperature dependence and implications for the stratosphere

Ultraviolet photodissociation of OCS: Product energy and angular distributions

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