Proper Time Delays Measured by Optical Streaking

Area of Science:

• Attosecond science
• Quantum dynamics
• Scattering theory

Background:

• Wigner-Smith time delays are widely used in attosecond science to probe electron dynamics.
• These time delays are typically measured using the streaking method.
• The direct experimental proof for this measurement technique has been lacking.

Purpose of the Study:

• To rigorously derive and validate the relationship between Wigner-Smith time delays and streaking shifts.
• To identify the specific conditions under which streaking shifts accurately represent Wigner-Smith time delays.
• To propose a new, more reliable method for measuring time delays in electron dynamics.

Main Methods:

• Theoretical analysis of energy absorption during the streaking process.
• Derivation of the relationship between streaking shifts and Wigner-Smith time delays.
• Investigation of electron interactions, including those with long-range Coulomb tails.

Main Results:

• The study reveals that streaking shifts only measure Wigner-Smith time delays under specific conditions.
• For interactions with long-range Coulomb tails, finite streaking shifts can be misleading.
• A new definition for time delays and a simplified measurement technique are proposed.

Conclusions:

• The assumption that streaking shifts directly measure Wigner-Smith time delays is not universally valid.
• A refined theoretical framework is necessary for accurate time-delay measurements in attosecond science.
• The proposed new measurement technique offers a more reliable approach, avoiding complete streaking scans.