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Effect of spin-orbit coupling on high-order harmonic generation in atoms
Optics Express
|July 30, 2025
Summary
Spin-orbit coupling (SOC) significantly alters high-order harmonic generation (HHG) from excited states in hydrogen atoms, but not the ground state. The ml=0 component dominates harmonic yields, while ml=1 influences lower-energy harmonics.
Area of Science:
- Quantum mechanics
- Atomic physics
- Nonlinear optics
Background:
- High-order harmonic generation (HHG) is a crucial process for producing extreme ultraviolet and X-ray radiation.
- Spin-orbit coupling (SOC) is a relativistic effect that can influence atomic electronic structure and dynamics.
Purpose of the Study:
- To investigate the influence of spin-orbit coupling (SOC) on high-order harmonic generation (HHG) in hydrogen atoms.
- To analyze the role of spin-split excited states in HHG spectra.
Main Methods:
- Numerical solution of the time-dependent Schrödinger equation including SOC (TDSE-SOC).
- Development of a modified strong-field approximation theory incorporating spin-split states.
Main Results:
- SOC does not affect HHG spectra from the ground state.
- Significant variations in harmonic yields are observed for excited 2P states (2P3/2 and 2P1/2) due to SOC.
- The ml=0 component in spin-split 2P states predominantly contributes to harmonic yields.
- The ml=1 component influences lower-energy harmonics in linearly polarized laser fields.
Conclusions:
- SOC plays a critical role in HHG from excited atomic states.
- The developed theoretical model qualitatively agrees with numerical simulations.
- Understanding SOC effects is essential for controlling and optimizing HHG spectra.
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