Talks and seminars

Abstract: The nuclear dynamics and spectroscopy of the NO3 radical is still not fully understood despite multiple theoretical
and experimental investigations over the last few decades. Experimentally, the Neumark group made breakthroughs by recording in 1991¹ the first photodetachment spectra of the nitrate anion (NO⁻₃), then in 2020 by providing a cryogenic cooling version of these spectra² and more recently in 2024³ when they added more hot bands by selective excitation of the anion within the IR-cryo-SEVI technique. Other groups, for example the Kawaguchi group,⁴ work on precise IR spectroscopies. The interpretation of these spectra requires a complete, detailed modelling of the five lowest potential energy surfaces of the NO3 radical.In my talk, I will present the scheme we have been developing over the past 20 years to simu­late from first principles the photodetachment spectrum of the nitrate anion and the IR spectrum of the nitrate radical. This scheme relies on the determination of accurate full-dimensional coupled diabatic potential energy surfaces adjusted to high quality ab initio energies via an artificial neural network-based scheme.MCTDH is used to propagate full dimensional wave-packets designed such that temperature effects and the impact of near threshold detachment are taken into account. ^5,6 The ten­sor network state method as developed by H. R. Larsson provides important insights necessary for interpreting the IR spectra.⁷

1. Weaver, A., Arnold, D. W., Bradforth, S. E. and Neumark, D. M. Examination of the ²A^'₂ and 2E'' states of NO3 by UV photoelectron spectroscopy of NO⁻₃. J. Chem. Phys. 94, 1740 (1991).
2. Babin, M.C., DeVine, J. A., DeWitt, M., Stanton J. F. and Neumark, D. M. High-Resolution Photoelectron Spectroscopy of Cryogenically Cooled NO⁻₃. J. Phys. Chem. Lett. 11, 395 (2020).
3. Lau, J.A., DeWitt, M., Frank, P.R., Stanton J. F. and Neumark, D. M. High-Resolution Photo­electron Spectroscopy of NO⁻₃ vibrationally excited along its ν3 mode. pre-print , (2024).
4. Kawaguchi, K., Fujimori, R. and Ishiwata, T. Infrared Spectroscopy of the NO3 radical from 2000 to 3000 cm⁻¹. J. Mol. Spectrosc. 344, 6 (2018).
5. Viel, A., Williams, D. M. G. and Eisfeld, W. Accurate quantum dynamics simulation of the photodetachment spectrum of the nitrate anion (NO3) based on an artificial neural network diabatic potential model. J. Chem. Phys. 154, 084302 (2021).
6. Williams, D. M. G., Viel, A. and Eisfeld, W. Simulation of the photodetachment spectra of the nitrate anion (NO⁻₃) in the B²E' energy range and non-adiabatic electronic population dynamics of NO3. Phys. Chem. Chem. Phys. 24, 24706 (2022).
7. Larsson, H. R. and Viel, A. 2500 vibronic eigenstates of the NO3 radical. Phys. Chem. Chem. Phys. 26, 24506 (2024).

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