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USER-FRIENDLY INTERFACESFOR ELECTRON SCATTERING

AND PHOTOIONIZATION CALCULATIONS

Maria Tudorovskaya, Quantemol Ltd.

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Background Fields where electron/light scattering matters:

Low-temperature plasma physics for etching, deposition, sputtering (semiconductors)

● High-harmonic generation ● Photoelectron spectroscopy

● Combustion; Fusion plasmas; Medical plasma; ● Lightning and laser industry; ● Atmospheric plasma & Astrophysics;

Quantemol has developed user-friendly software to help out

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QN/QEC processes

● Choose whether to “freeze” electrons or allow excitations● Molpro for optimization● + Additional methods

Elastic& inelasticAB + e AB +e

AB + e AB* + e

Rotational excitationAB(N’) + e AB(N’’) + e

Dissociative attachment AB + e A- + B

Impact ionization (e,2e)

AB + e AB+ + 2e

Photoionization*AB + hν AB+ + e

Non-UKRMol

*Will be a separate software

High-energy elastic& inelasticAB + e AB +e

AB + e AB* + e

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Electron-collision interfaces

Quantemol Electron Collision: an expert system for performing UKRmol+ electron – molecule collision calculations

B. Cooper, M. Tudorovskaya, S. Mohr, A O’Hare, M. Hanicinec, A. Dzarasova, J. Gorfinkiel, J. Benda, Z. Masin, A. Al-Refaie, P J Knowles, J. Tennyson

In preparation, 2019

Quantemol-N: an expert system for performing electron – molecule collision calculations using the R-matrix method

J. Tennyson, D. Brown, J J Munro, I Rozum, H N Varambhia, and N Vinci

J. Phys.: Conf. Ser.86 012001 2007

UKRmol/Java UKRMol+/Python

An upgraded product for faster calculations & bigger molecules

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Sign up for the newsletter at quantemol.com to learn about the upcoming publication

Contact support@quantemol.com for a free trial

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Calculation setup

Molecular geometry Needed

Optimized!(Molpro)

Information on molecular symmetry Needed Automatic(Molpro)

Method:

● Static exchange (for elastic scattering)● Static exchange with polarization (+1 e- in

CAS)● Close coupling (excitations)

✔✔✔

✔✔✔

Complete active space Flexible Autogenerated(Molpro)

& flexible

Flexible R-matrix sphere size ✔ ✔

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Additional features: I. High-energy scattering

Spherical Complex Optical Potential method

High-energy electrons! (~103 eV)Molpro: charge density to contstruct the real part

Figure: J Hamilton 2017N

2 elastic and inelastic

Compared to:A Jain & K L BalujaPhys. Rev. A, 45(1):202–218,1992

AB + e- AB or AB*

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Additional features:II. Dissociative e- attachment

Low energies → first step in plasmas; Semi-empirical via resonance (UKRmol(+) routine RESON)

R-matrix: resonance positions, width

Cross section i ~ Breit-Wigner

AB + e- AB- A + B-

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Additional features:III. e-– impact ionization

Binary Encounter Bethe: Dipole interaction between incident & ionized electrons

No external parameters! From Molpro:

● T: incident e- kinetic energy ● B: binding energy of sub-shell e-

● U: average e- kinetic energy

AB + e- AB-

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Validation: inelastic

“..anionic atoms are important in the etching of semiconductor wafers”

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Validation: photodetachment

“...detected in interstellar clouds”

AB- + hν AB + e-

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Validation: photoionization

Partial photoionization cross sections

BrO2

-

Pulse at certain photon energy!

● States 0 and 1 contribute the most!● Start at ~I

p● Single-photon regime: Ekin = ω – Ip● σ(ω) →σ(E

kin)

● Photoelectron signal:S(E

kin) = ∑

i σ(E

kin) ε{E

kin – (ωpump - I

pi)}

AB + hν AB+ + e-

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Partial photoionization cross sections

BrO2

- Validation: photoionization

AB + hν AB+ + e-

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More results:Ketene, H2C2O

● Interesting molecule…

● Also: in 2018, observed for the first time during plasma catalysis at atmospheric pressure in CO

2/CH

4/N

2 mixture

”...ketenes and their dimers are important reactants that find use in the production of a wide range of chemicals in a diverse range of industries including pigments, pharmaceuticals and agrochemicals and as intermediates for the paper industry.”

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Ketene: elastic scattering/excitation

Cross-sections may be used for simulations of the experimental plasma

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Ketene: other cross sectionsRotational excitation

Differential cross sections

String forward peak: typical for a molecule with a dipole

2 eV, 4.5 eV resonances: the molecule forgets all information about the electron direction

Energy

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Dissociative recombinationAB+ + e- AB* A + BImportant in extraterrestrial, atmospheric chemistry….

● Rotation is neglected● The cross section is averaged

over autoionizing resonances● Autoionization lifetime is assumed >> predissociation lifetime● The harmonic approximation for the vibrational states of the core ion● Small changes in the geometry for the partial derivatives

Example: HeH+

[1] Rolf Güsten, et al. Nature 568, (2019) 357–359[2] S. Fonseca dos Santos, N. Douguet, V. Kokoouline, A. E. Orel, J. Chem. Phys. 140, (2014), 164308[3] J. Tennyson, et al. J. Phys.: Conf. Ser. 86, (2007), 012001[4] Mehdi Ayouz, Viatcheslav Kokoouline, Atoms. 4(4) (2016) 30

Aran O’Hare

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Coming soon

In QEC:● Effective core potentials for heavy metals● Vibrational excitation● Integration with the database:

● Light scattering for the spectroscopy community

As a separate product:

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Thanks Quantemol team!

Bridgette Cooper Jonathan Tennyson

Maria Tudorovskaya

Anna Dzarasova

Sebastian Mohr

Aran O’Hare

Martin Hanicinec

Daniel Brown

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Acknowledgements

● UKRmol developers:

Jimena Gorfinkiel and Alex Harvey and Jakub Benda and Zdenek Masin and Ahmed Al-Refaie… and many more

● Molpro developers:Hans-Joachim Werner, Peter J Knowles et al

● University College London

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THANKS!We are open for comments and suggestions

More: hands-on session with Bridgette Cooper