Attoseconds

An attosecond is a unit of time equal to 10^-18 seconds, the timescale used to study electron dynamics in atoms and molecules. In this interval, light travels about 0.3 nanometers, roughly the size of an atom, making attoseconds the natural scale for observing ultrafast electronic motion.

Attosecond pulses are produced primarily by high-harmonic generation, in which intense femtosecond laser pulses interact with noble gases to emit a broad spectrum in the extreme ultraviolet. By controlling the driving pulse and phase matching, researchers have achieved pulses on the order of tens to a few hundred attoseconds and generated isolated attosecond pulses for time-resolved measurements.

Measuring and timing attosecond-scale events rely on techniques such as attosecond streaking and reconstruction by attosecond beating by interference of two-photon transitions (RABBIT). These methods combine ultrafast extreme-ultraviolet pulses with synchronized infrared fields to map the timing of electron emission and to characterize the pulse shape and duration.

Applications of attosecond science include tracking photoelectron emission, observing electron wave packet dynamics, and studying charge migration in atoms, molecules, and solids. Attosecond spectroscopy provides insights into fundamental quantum processes, including ionization delays and electron correlation effects, and supports advances in chemistry, physics, and materials science.

Challenges remain in generating brighter, isolated attosecond pulses with precise timing, improving metrology and synchronization, and extending capabilities to more complex systems. Ongoing developments aim to broaden the practical reach and reliability of attosecond techniques.