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Even-harmonic generation due to beyond-Born-Oppenheimer dynamics
1Institut für Theoretische Physik, Am Hubland, 97074 Würzburg, Germany.
Physical Review Letters
|September 5, 2001
Summary
Unequal nuclear masses in HD molecules generate even harmonic generation during strong laser pulses, an effect missed by the Born-Oppenheimer approximation. These even harmonics are comparable in strength to odd harmonics at high frequencies.
Area of Science:
- Quantum optics
- Molecular physics
- Nonlinear optics
Background:
- High harmonic generation (HHG) is a key process in nonlinear optics.
- The Born-Oppenheimer approximation is a standard approach in molecular physics, but it has limitations.
Purpose of the Study:
- To investigate the harmonic spectrum generated by a model HD molecule in a strong laser pulse.
- To explore the role of unequal nuclear masses in high harmonic generation.
- To determine if the Born-Oppenheimer approximation can capture this effect.
Main Methods:
- Numerical calculation of the harmonic spectrum.
- Modeling a hydrogen-deuterium (HD) molecule interacting with a strong laser field.
Main Results:
- The model HD molecule emitted even harmonics, which are photon frequencies that are even multiples of the laser frequency.
- This even harmonic emission was not observed within the Born-Oppenheimer approximation.
- In the high-frequency range, the intensity of even harmonics was comparable to that of odd harmonics.
Conclusions:
- Unequal nuclear masses in molecules are crucial for understanding high harmonic generation.
- The Born-Oppenheimer approximation is insufficient to describe phenomena involving nuclear motion, such as even harmonic generation.
- This finding opens new avenues for controlling and utilizing high harmonic generation for molecular studies.