| attosecond physics | |
|---|---|
| Name | Attosecond physics |
| Focus | Study of processes on the attosecond timescale |
| Discipline | Atomic physics, Optics, Quantum mechanics |
| Institutions | Max Planck Institute for Quantum Optics, Lawrence Berkeley National Laboratory, University of Freiburg, Imperial College London |
| Notable events | Attosecond pulse generation |
attosecond physics
Attosecond physics is the branch of ultrafast science that investigates electronic and nuclear motion on the attosecond (10^−18 second) timescale. It provides experimental and theoretical access to quantum dynamics in atoms, molecules and solids, enabling direct observation and control of processes governed by Quantum mechanics and Atomic physics that were previously inferred only indirectly.
Attosecond physics emerged from advances in high-intensity laser technology and nonlinear optics during the late 20th and early 21st centuries. Key milestones include the development of high-order harmonic generation (HHG) as demonstrated by researchers at institutions such as the Max Planck Institute for Quantum Optics and groups led by Paul B. Corkum and Pierre Agostini. The first isolated attosecond pulses were reported in the early 2000s, catalyzing experiments at facilities like Lawrence Berkeley National Laboratory and university laboratories worldwide. Awards such as the Wolf Prize in Physics and the Nobel Prize in Physics recognized related advances in ultrafast laser science, while conferences including the Conference on Quantum Electronics and the CLEO meeting served as forums for rapid dissemination.
Attosecond physics focuses on dynamics faster than femtosecond chemical bond rearrangements and comparable to electron correlation and tunneling times. Fundamental concepts include the attosecond as a unit, electron wavepackets, and phenomena such as photoionization time delays, electron correlation, and tunneling ionization in strong fields described by Time-dependent Schrödinger equation frameworks. Timescales span from tens to hundreds of attoseconds for single-electron dynamics up to few-femtosecond scales when coupling to nuclear motion (e.g., vibrational dynamics studied in Molecular physics). The field interfaces with Quantum optics for photon–electron interactions and with Solid-state physics when addressing ultrafast carriers in materials like graphene and silicon.
Generation of attosecond pulses primarily relies on High-order harmonic generation in gases driven by femtosecond intense lasers, often using carrier-envelope phase (CEP) stabilized pulses from systems such as chirped-pulse amplification (CPA) amplifiers. Alternatives include free-electron laser schemes at facilities like the European XFEL and Linac Coherent Light Source for extreme-ultraviolet (XUV) and x-ray attosecond sources. Characterization methods include attosecond streaking, reconstruction of attosecond beating by interference of two-photon transitions (RABBITT), and spectral phase retrieval techniques; these were developed in labs associated with researchers like Ferenc Krausz and Margaret Murnane. Detector and beamline technologies from organizations such as National Institute of Standards and Technology support accurate temporal calibration.
Attosecond pulses enable direct measurement of photoemission delays, intra-atomic electron correlation dynamics, and charge migration in molecules immediately following ionization. Experiments have probed Wigner time delays in photoionization, many-body effects described by Configuration interaction and Time-dependent density functional theory, and ultrafast Auger decay processes. Studies of atoms such as helium and argon have served as benchmarks, while molecular systems like benzene and biological chromophores reveal charge redistribution relevant to photochemistry and radiation damage. Attosecond techniques access coherent electron motion, offering time-resolved views of processes foundational to Quantum chemistry.
Primary experimental techniques include attosecond streaking spectroscopy, RABBITT, transient absorption in the XUV, and pump–probe schemes combining attosecond pulses with infrared (IR) or visible probes. Laboratories use carrier-envelope-phase control, polarization gating, and adaptive pulse shaping to produce isolated attosecond pulses. Beamlines at national laboratories and university facilities employ vacuum-ultraviolet optics, grazing-incidence mirrors, and time-of-flight electron spectrometers. Cross-disciplinary collaborations with groups in Chemical physics and Materials science integrate attosecond methods into studies of non-equilibrium dynamics and ultrafast magnetism, often presented at the American Physical Society meetings.
Theoretical descriptions span ab initio methods solving the time-dependent Schrödinger equation for few-electron systems, many-body perturbation theory, and time-dependent density functional theory (TDDFT) adapted for strong-field and attosecond regimes. Semiclassical models such as the three-step model of HHG and saddle-point methods provide intuition for electron trajectories. Numerical techniques include grid-based propagation, complex scaling for continuum states, and discrete-variable representations; computational efforts often leverage supercomputing centers at institutions like Lawrence Livermore National Laboratory and university clusters. Accurate modeling must account for electron correlation, relativistic corrections for x-ray regimes, and coupling to nuclear motion where relevant.
Attosecond science contributes to fundamental understanding and potential technologies: probing charge migration could inform molecular electronics and photochemistry, while attosecond-resolved photoemission informs ultrafast electronics and spintronic device design. Development of attosecond x-ray sources impacts time-resolved crystallography and studies at facilities such as European XFEL. Industrial and medical applications remain exploratory but include radiation chemistry control and ultrafast metrology. Continued progress in laser engineering, beamline technology, and theory promises integration with quantum information science and advanced materials research.
Category:Quantum physics Category:Ultrafast science