A theoretical and experimental study of pressure broadening of the oxygen A-band by helium

Grimminck, Dennis L.A.G.; Spiering, Frans R.; Janssen, Liesbeth M. C.; Avoird, Ad van der; Zande, Wim J. van der; Groenenboom, Gerrit C.

doi:10.1063/1.4878666

Cited by 8 publications

(7 citation statements)

References 54 publications

(77 reference statements)

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“…Here, we point out two aspects of the electronic wavefunction which are implicit in the notation of Eq. (5). First of all, the electronic wavefunction is anti-symmetric with respect to the exchange of any two electrons, which is accomplished by acting on Eq.…”

Section: A Monomer Electronic States and The Diabatic Modelmentioning

confidence: 99%

Potential energy and dipole moment surfaces of the triplet states of the O2(X3Σg−) − O2(X3Σg−,a1Δg,b1Σg+) complex

Karman¹,

Avoird²,

Groenenboom³

2017

The Journal of Chemical Physics

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We compute four-dimensional diabatic potential energy surfaces and transition dipole moment surfaces of O-O, relevant for the theoretical description of collision-induced absorption in the forbidden XΣ → aΔ and XΣ → bΣ bands at 7883 cm and 13 122 cm, respectively. We compute potentials at the multi-reference configuration interaction (MRCI) level and dipole surfaces at the MRCI and complete active space self-consistent field (CASSCF) levels of theory. Potentials and dipole surfaces are transformed to a diabatic basis using a recent multiple-property-based diabatization algorithm. We discuss the angular expansion of these surfaces, derive the symmetry constraints on the expansion coefficients, and present working equations for determining the expansion coefficients by numerical integration over the angles. We also present an interpolation scheme with exponential extrapolation to both short and large separations, which is used for representing the O-O distance dependence of the angular expansion coefficients. For the triplet ground state of the complex, the potential energy surface is in reasonable agreement with previous calculations, whereas global excited state potentials are reported here for the first time. The transition dipole moment surfaces are strongly dependent on the level of theory at which they are calculated, as is also shown here by benchmark calculations at high symmetry geometries. Therefore, ab initio calculations of the collision-induced absorption spectra cannot become quantitatively predictive unless more accurate transition dipole surfaces can be computed. This is left as an open question for method development in electronic structure theory. The calculated potential energy and transition dipole moment surfaces are employed in quantum dynamical calculations of collision-induced absorption spectra reported in Paper II [T. Karman et al., J. Chem. Phys. 147, 084307 (2017)].

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Section: A Monomer Electronic States and The Diabatic Modelmentioning

confidence: 99%

Potential energy and dipole moment surfaces of the triplet states of the O2(X3Σg−) − O2(X3Σg−,a1Δg,b1Σg+) complex

Karman¹,

Avoird²,

Groenenboom³

2017

The Journal of Chemical Physics

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“…Note that the case of isotropic Raman Q branches of linear molecules is "simple" when vibrational effects are neglected, because the real off-diagonal elements of W are then simply the negative of the usual inelastic state-to-state collisional transfer rates. The oxygen A-band perturbed by helium was studied theoretically and experimentally in [201]. For the first time for an electronic transition, the relaxation matrix was obtained from a fully quantum mechanical approach, leading to good agreement with measurements.…”

Section: Quantal Approachesmentioning

confidence: 97%

“…For instance, these advanced computational capabilities have enabled, for H 2 -He, consideration of the effects of the centrifugal distortion of the PES or of rovibrational potential coupling terms [156,200]. PESs for the active molecule in the ground state or in an excited electronic state also have enabled calculations of pressure-broadening and -shifting coefficients for rotational, rovibrational and rovibronic lines [201,202]. Furthermore, CC predictions for asymmetric-top molecules in a bath of diatomics are nowadays feasible.…”

Section: Quantal Approachesmentioning

confidence: 99%

Recent advances in collisional effects on spectra of molecular gases and their practical consequences

Hartmann

Tran

Armante

et al. 2018

Journal of Quantitative Spectroscopy and Radiative Transfer

100

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“…Tran et al performed calculations of the relaxation matrix in the energycorrected sudden approximation for O 2 -O 2 and O 2 -N 2 14 and Grimminck et al calculated line-mixing using full coupledchannels calculations for the O 2 -He system. 15 In fact, the theoretical relaxation matrices computed by Tran et al 14 are used in the most recent and detailed analysis of the oxygen Aband for remote sensing. 16 For collision-induced absorption, the theory for rotation-translation spectra as well as vibrational transitions has been developed, but to our knowledge this theory has not before been extended to electronic transitions.…”

Section: Introductionmentioning

confidence: 99%

“…A second question is the nature of the mechanism leading to the breaking of spin symmetry and collision-induced absorption: Is it the exchange interaction with a second paramagnetic molecule or is it the monomer spin-orbit interaction? This is a fundamental question, but at a practical level, its answer determines whether one should expect collision-induced absorption due to O 2 -N 2 collisions to be negligible 15 or comparable 14 to O 2 -O 2 . Another aspect which may affect atmospheric applications is the temperature dependence of the collision-induced absorption spectrum.…”

Section: Introductionmentioning

confidence: 99%

Line-shape theory of the X3Σg−→a1Δg,b1Σg+ transitions in O2–O2 collision-induced absorption

Karman¹,

Avoird²,

Groenenboom³

2017

The Journal of Chemical Physics

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We derive the theory of collision-induced absorption for electronic transitions in the approximation of an isotropic interaction potential. We apply this theory to the spin-forbidden XΣ→aΔ and XΣ→bΣ transitions in O-O, which are relevant for calibration in atmospheric studies. We consider two mechanisms for breaking the spin symmetry, either by the intermolecular exchange interaction between paramagnetic collision partners or by the intramolecular spin-orbit coupling. The calculations for the exchange-based mechanism employ the diabatic potential energy surfaces and transition dipole moment surfaces reported in Paper I [T. Karman et al., J. Chem. Phys. 147, 084306 (2017)]. We show that the line shape of the theoretical absorption spectra is insensitive to the large uncertainty in the electronic transition dipole moment surfaces. We also perform calculations using a simple model of the alternative mechanism involving intramolecular spin-orbit coupling, which leads to absorption intensities which are well below the experimental results. The relative intensity of this spin-orbit-based mechanism may impact the relative contribution to the absorption by collisions with diamagnetic collision partners, such as the atmospherically relevant N molecule. We furthermore show that both the line shape and temperature dependence are signatures of the underlying transition mechanism.

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A theoretical and experimental study of pressure broadening of the oxygen A-band by helium

Abstract: The rotationally resolved magnetic dipole absorption spectrum of the oxygen A-band

Cited by 8 publications

References 54 publications

Potential energy and dipole moment surfaces of the triplet states of the O2(X3Σg−) − O2(X3Σg−,a1Δg,b1Σg+) complex

Potential energy and dipole moment surfaces of the triplet states of the O2(X3Σg−) − O2(X3Σg−,a1Δg,b1Σg+) complex

Recent advances in collisional effects on spectra of molecular gases and their practical consequences

Line-shape theory of the X3Σg−→a1Δg,b1Σg+ transitions in O2–O2 collision-induced absorption

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