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Updated: Mar 15, 2026

Excitonic Hamiltonians for Calculating Optical Absorption Spectra and Optoelectronic Properties of Molecular Aggregates and Solids
Published on: May 27, 2020
Circular RABBITT Goes under Threshold: A Sensitive Probe of Discrete Excitations in Noble Gas Atoms
Vladislav V Serov1, Jia-Bao Ji2, Meng Han3
1Saratov State University, Department of Medical Physics, Saratov 410012, Russia.
Abstract:
We introduce circular under-threshold RABBITT (cuRABBITT) as a new interferometric method to probe discrete electronic excitations in atoms with attosecond resolution. By combining circularly polarized attosecond pulses with broadband ("rainbow") spectral analysis, we directly access two-photon ionization amplitudes and their relative phases. Time-dependent Schrödinger simulations, supported by Green's function theory, reveal strong resonances in helium and argon and a Cooper-like minimum in xenon. These results demonstrate that cuRABBITT provides continuous spectral mapping of bound-state resonances and extends Fano's propensity rule into the under-threshold regime. Our Letter establishes cuRABBITT as a powerful attosecond metrology technique, opening the way to polarization-resolved studies of resonant dynamics in atoms and molecules.
Related Concept Videos
Noble Gases
The elements in group 18 are noble gases (helium, neon, argon, krypton, xenon, and radon). They earned the name “noble” because they were assumed to be nonreactive since they have filled valence shells. In 1962, Dr. Neil Bartlett at the University of British Columbia proved this assumption to be false.
The Aufbau Principle and Hund's Rule
Emission Spectra
The Bohr Model
Electron Configuration of Multielectron Atoms
Exceptions to the Octet Rule

