Theoretical developments for precision spectroscopy of polyatomic and polyelectronic molecules

Projektinformationen

POLYQUANT

ID Finanzhilfevereinbarung: 851421

DOI

10.3030/851421

Projekt abgeschlossen

EK-Unterschriftsdatum 5 November 2019

Startdatum 1 Januar 2020

Enddatum 31 August 2025

Finanziert unter

• EXCELLENT SCIENCE - European Research Council (ERC)

Gesamtkosten

€ 1 424 175,00

EU-Beitrag

€ 1 424 175,00

Koordiniert durch

EOTVOS LORAND TUDOMANYEGYETEM
Hungary

Periodic Reporting for period 4 - POLYQUANT (Theoretical developments for precision spectroscopy of polyatomic and polyelectronic molecules)

Berichtszeitraum: 2024-07-01 bis 2025-08-31

Zusammenfassung vom Kontext und den Gesamtzielen des Projekts

POLYQUANT developed molecular quantum theory by massively going beyond the traditional non-relativistic and Born-Oppenheimer approximations. Theoretical, methodological, and algorithmic developments have been carried out, computations have been performed for small molecular systems to high precision and the formerly neglected or unexplored non-adiabatic, relativistic and QED effects and couplings were scrutinized by comparison with high-resolution and precision spectroscopy experiments.

Arbeit, die ab Beginn des Projekts bis zum Ende des durch den Bericht erfassten Berichtszeitraums geleistet wurde, und die wichtigsten bis dahin erzielten Ergebnisse

Motivated by the recent increase in the energy resolution of the best (gas-phase, high-resolution) spectroscopy experiments, sophisticated control of molecular quantum states, and synchronisation of spectrometers to atomic clocks, it became necessary to develop ultra-precise quantum chemistry. Solving the existing equations more precisely was not sufficient; it was necessary to go beyond the two fundamental approximations, the Born-Oppenheimer and the non-relativistic approximations, common in molecular computations even today. In the POLYQUANT project, theoretical, algorithmic and methodological developments have been carried out along these lines. The newly-developed methodologies include the computation of 1) the non-adiabatic mass for isolated and coupled electronic states; 2) regularised leading-order relativistic corrections; 3) regularised leading-order QED corrections through the non-relativistic quantum electrodynamics framework; 4) rovibrational and rovibronic computations in diatomics, including non-adiabatic and relativistic and QED corrections and couplings; 5) rovibrational computations for modelling hyperfine and Zeeman effects in polyatomic systems. Furthermore, variational relativistic computations became possible with unprecedented accuracy, and a systematic study was conducted to compare and validate the variational relativistic results with respect to benchmark perturbative relativistic values. All in all, theoretical and methodological progress has been made towards an ultra-precise quantum chemistry framework that can keep up with the progress of ultra-precise spectroscopy and provide possible guidance for related fields, including quantum technology developments operating on a molecular platform or condensed-phase simulations considering non-adiabatic and magnetic effects.

Fortschritte, die über den aktuellen Stand der Technik hinausgehen und voraussichtliche potenzielle Auswirkungen (einschließlich der bis dato erzielten sozioökonomischen Auswirkungen und weiter gefassten gesellschaftlichen Auswirkungen des Projekts)

In POLYQUANT, theoretical and computational approaches have been developed to compute non-adiabatic, relativistic and quantum-electrodynamical (QED) corrections and couplings in molecular systems. Through a series of computational applications, these often neglected and largely unexplored physical effects have been scrutinised by comparing the computational results with high-resolution (gas-phase) spectroscopy experiments. As a result of the work, novel methodologies and benchmark data became available for using, designing and interpreting new experiments and developing modelling tools for larger systems.

POLYQUANT summary