An <i>ab initio</i> study of the rovibronic spectrum of sulphur monoxide (SO): diabatic <i>vs.</i> adiabatic representation

Brady, Ryan P.; Yurchenko, Sergey; Kim, Gap‐Sue; Somogyi, Wilf; Tennyson, Jonathan

doi:10.1039/d2cp03051a

Cited by 15 publications

(11 citation statements)

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“…We find some weak-to-moderate (2.5 σ ) evidence of SO (ref. 82 ) and no evidence of SO 3 (ref. 83 ), qualitatively matching the photochemical model predictions.…”

Section: Methodsmentioning

confidence: 99%

Sulfur dioxide in the mid-infrared transmission spectrum of WASP-39b

Powell,

Feinstein,

Lee

et al. 2024

Nature

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The recent inference of sulfur dioxide (SO2) in the atmosphere of the hot (approximately 1,100 K), Saturn-mass exoplanet WASP-39b from near-infrared JWST observations1–3 suggests that photochemistry is a key process in high-temperature exoplanet atmospheres4. This is because of the low (<1 ppb) abundance of SO2 under thermochemical equilibrium compared with that produced from the photochemistry of H2O and H2S (1–10 ppm)4–9. However, the SO2 inference was made from a single, small molecular feature in the transmission spectrum of WASP-39b at 4.05 μm and, therefore, the detection of other SO2 absorption bands at different wavelengths is needed to better constrain the SO2 abundance. Here we report the detection of SO2 spectral features at 7.7 and 8.5 μm in the 5–12-μm transmission spectrum of WASP-39b measured by the JWST Mid-Infrared Instrument (MIRI) Low Resolution Spectrometer (LRS)10. Our observations suggest an abundance of SO2 of 0.5–25 ppm (1σ range), consistent with previous findings4. As well as SO2, we find broad water-vapour absorption features, as well as an unexplained decrease in the transit depth at wavelengths longer than 10 μm. Fitting the spectrum with a grid of atmospheric forward models, we derive an atmospheric heavy-element content (metallicity) for WASP-39b of approximately 7.1–8.0 times solar and demonstrate that photochemistry shapes the spectra of WASP-39b across a broad wavelength range.

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“…We find some weak-to-moderate (2.5 σ ) evidence of SO (ref. 82 ) and no evidence of SO 3 (ref. 83 ), qualitatively matching the photochemical model predictions.…”

Section: Methodsmentioning

confidence: 99%

Sulfur dioxide in the mid-infrared transmission spectrum of WASP-39b

Powell,

Feinstein,

Lee

et al. 2024

Nature

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“…Its curves have complex shapes with the model being very sensitive to the mutual consistency of the curves V 1 a , V 2 a , and W 12 (1) around the crossing point. The disadvantage of the diabatic representation is that it does not come out as a solution of the (adiabatic) electronic structure calculations directly and needs to be constructed either through a diabatization approach ,,− or approximated.…”

Section: Solving the Rovibronic Schrödinger Equations For Ch And Yomentioning

confidence: 99%

“…The so-called derivative couplings (DDRs) or nonadiabatic couplings (NACs) between states that exhibit avoided crossings arise through the nuclear kinetic energy operator acting on the electronic wave functions when the BO approximation is relaxed and corresponds to derivatives in terms of the nuclear coordinate. The computation of DDRs and PESs around the avoided crossing geometry is a major source of computational expense within both quantum chemistry and nuclear motion calculations because of the cusp-like behavior of the PESs and the singular nature of the DDRs at the geometry of spatial degeneracy. ,− It is therefore the main focus of many works to explore property-based diabatization methods ,− that transform to a diabatic representation, where DDRs vanish or are reduced and PESs become smooth. For diatomics, the smoothness condition of their PECs uniquely defines the unitary transformation to the diabatic representation where NACs (first-order nondiagonal DDR) vanish, PECs are allowed to cross, and consequently, the molecular properties are smooth, at the cost of introducing off-diagonal diabatic potential couplings.…”

Section: Introductionmentioning

confidence: 99%

Numerical Equivalence of Diabatic and Adiabatic Representations in Diatomic Molecules

Brady,

Drury,

Yurchenko

et al. 2024

J. Chem. Theory Comput.

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The (time-independent) Schrodinger equation for atomistic systems is solved by using the adiabatic potential energy curves (PECs) and the associated adiabatic approximation. In cases where interactions between electronic states become important, the associated nonadiabatic effects are taken into account via derivative couplings (DDRs), also known as nonadiabatic couplings (NACs). For diatomic molecules, the corresponding PECs in the adiabatic representation are characterized by avoided crossings. The alternative to the adiabatic approach is the diabatic representation obtained via a unitary transformation of the adiabatic states by minimizing the DDRs. For diatomics, the diabatic representation has zero DDR and nondiagonal diabatic couplings ensue. The two representations are fully equivalent and so should be the rovibronic energies and wave functions, which result from the solution of the corresponding Schrodinger equations. We demonstrate (for the first time) the numerical equivalence between the adiabatic and diabatic rovibronic calculations of diatomic molecules using the ab initio curves of yttrium oxide (YO) and carbon monohydride (CH) as examples of two-state systems, where YO is characterized by a strong NAC, while CH has a strong diabatic coupling. Rovibronic energies and wave functions are computed using a new diabatic module implemented in the variational rovibronic code DUO. We show that it is important to include both the diagonal Born−Oppenheimer correction and nondiagonal DDRs. We also show that the convergence of the vibronic energy calculations can strongly depend on the representation of nuclear motion used and that no one representation is best in all cases.

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“…In principle, either the adiabatic or diabatic representation can be used to describe the PECs with avoided crossing. However, the adiabatic PECs have singularities near the crossing points [62], leading to lower fitting accuracy of the PECs and less numerical robustness in collision integral calculations. Moreover, based on the Landau-Zener method [63], an earlier calculation for nitrogen showed that the diabatic paths in collisions are much more likely to be followed than the adiabatic paths through the avoided crossing [58].…”

Section: Ab Initio Calculations Of Pecsmentioning

confidence: 99%

“…where the superscripts d and a refer to the diabatic and adiabatic bases, respectively, and θ is the nonadiabatic mixing angle which can be calculated by integrating the nonadiabatic coupling terms (NACTs) ⟨Ψ ad i |∂/∂R|Ψ ad j ⟩ or the CI vector method [62,65,66]. In this work, the CI vectors method is used for the avoided crossings due to the two-state coupling.…”

Section: Ab Initio Calculations Of Pecsmentioning

confidence: 99%

Collision integrals of electronically excited atoms in air plasmas. I. N–N and O–O interactions

Zhao,

Hong,

Yang

et al. 2023

Plasma Sources Sci. Technol.

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The current work presents the collision integral data for N(4 S)–N(4 S, 2 D, 2 P) and O(3 P, 1 D, 1 S)–O(3 P, 1 D, 1 S) interactions in the temperature range of 500–50 000 K. The collision integrals are calculated based on high-quality potential energy curves (PECs) obtained from fitting the high-level a b i n i t i o calculation data in a wide energy range to the neural network (NN) functions. In the construction of PECs, the diabatic PECs are adopted when avoided crossings exist because the diabatic paths are much more likely to be followed for such situations. Moreover, the nonadiabatic transition effects are estimated to be negligible for PECs crossings. The accuracy of traditional analytical formulas to fit PECs are also examined. It is found that the collision integral calculations are sensitive to the accuracy of PECs and the NN based PECs overwhelm the others. The contribution of inelastic excitation exchange processes to the diffusion collision integrals are also computed by using an accurate evaluation of the differences of PECs for gerade and ungerade pairs of excited atoms. Finally, based on the new collision integral data, we calibrate the collision model parameters suitable for the widely used particle simulation methods. The collision integrals and collision models developed in this work can be used to support high-confidence simulations of weakly ionized air plasma problems.

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An ab initio study of the rovibronic spectrum of sulphur monoxide (SO): diabatic vs. adiabatic representation

Abstract: e present an ab initio study of the rovibronic spectra of sulphur monoxide using internally contracted multireference configuration interaction (ic-MRCI) method using aug-cc-pV5Z basis sets. It covers 13 lowest electronic...

Cited by 15 publications

References 91 publications

Sulfur dioxide in the mid-infrared transmission spectrum of WASP-39b

Sulfur dioxide in the mid-infrared transmission spectrum of WASP-39b

Numerical Equivalence of Diabatic and Adiabatic Representations in Diatomic Molecules

Collision integrals of electronically excited atoms in air plasmas. I. N–N and O–O interactions

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