Continuous rainbow RABBITT investigation of resonant states in He and H$_2$

TL;DR

This study uses rainbow RABBITT, an advanced attosecond spectroscopy technique, to resolve and analyze resonant states in helium and hydrogen molecules with high energy resolution, enabling continuous reconstruction of resonance series.

Contribution

The paper introduces a novel application of rainbow RABBITT for continuous, simultaneous reconstruction of resonance series in atoms and molecules without adjusting laser frequency.

Findings

Successful resolution of under-threshold and above-threshold resonances

Efficient extraction of RABBITT phase and magnitude parameters

Validation of the logarithmic Hilbert transform in resonant regions

Abstract

We employ Reconstruction of Attosecond Beating By Interference of Two-photon Transitions with an advanced energy resolution (rainbow RABBITT) to resolve under-threshold discrete excitations and above-threshold auto-ionizing states in the He atom and the H$_2$ molecule. Both below and above the threshold, the whole series of resonances is reconstructed continuously and at once by the parity based separation of the two-photon ionization amplitude. This allows for an efficient extraction of the RABBITT magnitude and phase parameters without the need for adjusting the laser photon frequency. The latter parameters are then used to test the validity of the logarithmic Hilbert transform which relates the RABBITT phase and magnitude in the resonant region.