Odd-even high-order harmonic generation as a symmetry-resolved probe of intrinsic molecular asymmetry: From spectra to subcycle interferometry
Phys. Rev. A 114, 013109 – Published 9 July, 2026
DOI: https://doi.org/10.1103/ctnl-4zdg
Abstract
Odd-even high-order harmonic generation (HHG) from oriented polar molecules encodes intrinsic molecular asymmetry on a subcycle timescale, yet a complete set of amplitude-phase observables connecting spectral measurements to microscopic emission dynamics has remained elusive. In this study, we identify a complete amplitude-phase observable set linking spectral asymmetry, namely, odd-even intensity and phase difference, to amplitude and phase asymmetry of consecutive attosecond bursts through an explicit and invertible mapping. We show that these spectral and microscopic quantities provide equivalent signatures of molecular asymmetry within a subcycle interferometric picture, revealing parity-resolved electron rescattering cross sections associated with the symmetric and antisymmetric components of the molecular wave function. Numerical solutions of the time-dependent Schrödinger equation for oriented CO validate the proposed framework. These results establish odd-even HHG as a unified amplitude-phase probe of molecular asymmetry, enabling quantitative tracking of attosecond asymmetry dynamics directly from spectral measurements.
