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High Resolution Phonon-assisted Quasi-resonance Fluorescence Spectroscopy

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Near-threshold high-order harmonic spectroscopy with aligned molecules.

H Soifer¹, P Botheron, D Shafir

¹Department of Physics of Complex Systems, Weizmann Institute of Science, 76100 Rehovot, Israel.

Physical Review Letters

|January 15, 2011

Summary

We investigated high-order harmonic generation in molecules near the ionization threshold. Two distinct signals were observed, revealing new insights into molecular dynamics and spectroscopy.

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Area of Science:

Atomic, Molecular, and Optical Physics
Quantum Optics
Spectroscopy

Background:

High-order harmonic generation (HHG) is a crucial nonlinear optical process.
Understanding HHG near the ionization threshold is vital for advanced spectroscopy.
Molecular alignment significantly impacts HHG phenomena.

Purpose of the Study:

To investigate the origin of distinct contributions to high-harmonic generation in aligned molecules near the ionization threshold.
To analyze the influence of molecular alignment and driving field ellipticity on these contributions.
To explore the potential of extending high-harmonic spectroscopy to the near-threshold spectral range.

Main Methods:

Studying high-order harmonic generation in aligned molecules.
Analyzing two distinct contributions to the harmonic signal.
Performing classical electron trajectory analysis.
Considering the Coulomb potential's influence on electron dynamics.

Main Results:

Two distinct contributions to the harmonic signal were identified.
These contributions exhibited different responses to molecular alignment and field ellipticity.
The contributions were linked to primary ionization and excitation processes.
A deeper understanding of near-threshold harmonic generation origins was achieved.

Conclusions:

High-harmonic generation near the ionization threshold exhibits complex behavior with distinct contributing pathways.
Classical electron trajectory analysis, including Coulomb effects, is crucial for interpreting these dynamics.
High-harmonic spectroscopy can be effectively extended to the spectroscopically rich near-threshold region.