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Linear response in the strong field domain.

Alex C Han1, Moshe Shapiro

  • 1Department of Physics and Astronomy, The University of British Columbia, Vancouver V6T 1Z1, Canada.

Physical Review Letters
|June 12, 2012
PubMed
Summary
This summary is machine-generated.

Linear response in molecular systems does not always mean weak laser fields or first-order perturbation theory. Strong field effects can lead to linear photoexcitation yields and coherent control, challenging previous assumptions.

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Area of Science:

  • Physical Chemistry
  • Quantum Mechanics
  • Molecular Dynamics

Background:

  • First-order perturbation theory predicts linear response to external fields.
  • Linear response is commonly observed in experiments involving molecular systems and lasers.
  • Previous understanding suggested linear response implies weak fields and first-order perturbation theory.

Purpose of the Study:

  • To investigate the relationship between linear response and first-order perturbation theory in molecular photoexcitation.
  • To explore the possibility of linear response occurring under strong field conditions.
  • To analyze the role of shaped laser pulses in controlling molecular dynamics.

Main Methods:

  • Analysis of intensity dependence in photoexcitation, dissociation, and isomerization.
  • Computational modeling of molecular systems interacting with shaped broadband laser pulses.
  • Investigation of Raman transitions and their influence on photoexcitation yield and branching ratios.

Main Results:

  • Linear photoexcitation yield can be observed even with strong laser fields.
  • Coherent control over branching ratios is achievable in regimes previously thought impossible.
  • Continuum-mediated Raman transitions, combined with pulse shaping, can yield linear intensity dependence and significant coherent control.
  • The findings challenge the necessity of external bath effects to explain linear response with coherent control.

Conclusions:

  • Linear response does not necessitate weak external perturbations or adherence to first-order perturbation theory.
  • Strong field laser interactions can exhibit linear response characteristics.
  • Coherent control is possible in the linear response regime, even with single precursor states, by utilizing phenomena like Raman transitions and pulse shaping.