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Photoluminescence is light emission from any form of matter after the absorption of photons. It is one of many forms of luminescence and is initiated by photoexcitation, hence the prefix photo-. Following excitation, various relaxation processes typically occur in which other photons are re-radiated. Time periods between absorption and emission may vary: ranging from short femtosecond-regime for emission involving free-carrier plasma in inorganic semiconductors up to milliseconds for phosphoresence processes in molecular systems; and under special circumstances delay of emission may even span to minutes or hours.
A femtosecond is a unit of time in the International System of Units (SI) equal to 10-15 or 1⁄1 000 000 000 000 000 of a second; that is, one quadrillionth, or one millionth of one billionth, of a second. For context, a femtosecond is to a second as a second is to about 31.71 million years; a ray of light travels approximately 0.3 μm (micrometers) in 1 femtosecond, a distance comparable to the diameter of a virus.
Femtochemistry is the area of physical chemistry that studies chemical reactions on extremely short timescales in order to study the very act of atoms within molecules (reactants) rearranging themselves to form new molecules (products). In a 1988 issue of the journal Science, Ahmed Hassan Zewail published an article using this term for the first time, stating "Real-time femtochemistry, that is, chemistry on the femtosecond timescale...". Later in 1999, Zewail received the Nobel Prize in Chemistry for his pioneering work in this field showing that it is possible to see how atoms in a molecule move during a chemical reaction with flashes of laser light.
In physics and physical chemistry, time-resolved spectroscopy is the study of dynamic processes in materials or chemical compounds by means of spectroscopic techniques. Most often, processes are studied after the illumination of a material occurs, but in principle, the technique can be applied to any process that leads to a change in properties of a material. With the help of pulsed lasers, it is possible to study processes that occur on time scales as short as 10−16 seconds. All time-resolved spectra are suitable to be analyzed using the two-dimensional correlation method for a correlation map between the peaks.
Quantum optics is a branch of atomic, molecular, and optical physics dealing with how individual quanta of light, known as photons, interact with atoms and molecules. It includes the study of the particle-like properties of photons. Photons have been used to test many of the counter-intuitive predictions of quantum mechanics, such as entanglement and teleportation, and are a useful resource for quantum information processing.
In quantum chemistry, a conical intersection of two or more potential energy surfaces is the set of molecular geometry points where the potential energy surfaces are degenerate (intersect) and the non-adiabatic couplings between these states are non-vanishing. In the vicinity of conical intersections, the Born–Oppenheimer approximation breaks down and the coupling between electronic and nuclear motion becomes important, allowing non-adiabatic processes to take place. The location and characterization of conical intersections are therefore essential to the understanding of a wide range of important phenomena governed by non-adiabatic events, such as photoisomerization, photosynthesis, vision and the photostability of DNA. The conical intersection involving the ground electronic state potential energy surface of the C6H3F3+ molecular ion is discussed in connection with the Jahn–Teller effect in Section 13.4.2 on pages 380-388 of the textbook by Bunker and Jensen.
Ultrafast laser spectroscopy is a spectroscopic technique that uses ultrashort pulse lasers for the study of dynamics on extremely short time scales. Different methods are used to examine the dynamics of charge carriers, atoms, and molecules. Many different procedures have been developed spanning different time scales and photon energy ranges; some common methods are listed below.
The Max Planck Institute for Solid State Research was founded in 1969 and is one of the 82 Max Planck Institutes of the Max Planck Society. It is located on a campus in Stuttgart, together with the Max Planck Institute for Intelligent Systems.
The Journal of Physics B: Atomic, Molecular and Optical Physics is a biweekly peer-reviewed scientific journal published by IOP Publishing. It was established in 1968 from the division of the earlier title, Proceedings of the Physical Society. In 2006, the Journal of Optics B: Quantum and Semiclassical Optics was merged with the Journal of Physics B. The editor-in-chief is Marc Vrakking.
The College of Natural Science (NatSci) at Michigan State University is home to 27 departments and programs in the biological, physical and mathematical sciences.
The International Max Planck Research School for Ultrafast Imaging and Structural Dynamics (IMPRS-UFAST) is a graduate school of the Max Planck Society. It is a joint venture of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD), the University of Hamburg, the Center for Free Electron Laser Science, the Deutsches Elektronen Synchrotron (DESY), and the European XFEL GmbH. It was established in 2011 and is now based at the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg, Germany.
Ultrafast X-rays or ultrashort X-ray pulses are femtosecond x-ray pulses with wavelengths occurring at interatomic distances. This beam uses the X-ray's inherent abilities to interact at the level of atomic nuclei and core electrons. This ability combined with the shorter pulses at 30 femtosecond could capture the change in position of atoms, or molecules during phase transitions, chemical reactions, and other transient processes in physics, chemistry, and biology.
Kenji Ohmori is a Japanese physicist and chemist. National Institutes of Natural Sciences, Japan (NIMS), Institute for Molecular Science (IMS)
Philip H. Bucksbaum is an American atomic physicist, the Marguerite Blake Wilbur Professor in Natural Science in the Departments of Physics, Applied Physics, and Photon Science at Stanford University and the SLAC National Accelerator Laboratory. He also directs the Stanford PULSE Institute.
Ultrafast electron diffraction (UED), also known as femtosecond electron diffraction (FED), is a pump-probe experimental method based on the combination of optical pump-probe spectroscopy and electron diffraction. UED provides information on the dynamical changes of the structure of materials. It is very similar to time resolved crystallography, but instead of using X-rays as the probe, it uses electrons. In the UED technique, a femtosecond (fs) laser optical pulse excites (pumps) a sample into an excited, usually non-equilibrium, state. The pump pulse may induce chemical, electronic or structural transitions. After a finite time interval, a fs electron pulse is incident upon the sample. The electron pulse undergoes diffraction as a result of interacting with the sample. The diffraction signal is, subsequently, detected by an electron counting instrument such as a CCD camera. Specifically, after the electron pulse diffracts from the sample, the scattered electrons will form a diffraction pattern (image) on a CCD camera. This pattern contains structural information about the sample. By adjusting the time difference between the arrival of the pump and probe beams, one can obtain a series of diffraction patterns as a function of the various time differences. The diffraction data series can be concatenated in order to produce a motion picture of the changes that occurred in the data. UED can provide a wealth of dynamics on charge carriers, atoms, and molecules.
Mark Maroncelli is an American chemist, currently serving as professor of chemistry at the Pennsylvania State University, where he also coordinates the Chemistry Department's undergraduate program.
Michael David Fayer is an American chemical physicist. He is the David Mulvane Ehrsam and Edward Curtis Franklin Professor of Chemistry at Stanford University.
Albert Stolow is a Canadian physicist. He is the Canada Research Chair in Molecular Photonics, full professor of chemistry & biomolecular sciences and of physics, and a member of the Ottawa Institute for Systems Biology at the University of Ottawa. He is the founder and an ongoing member of the Molecular Photonics Group at the National Research Council of Canada. He is adjunct professor of Chemistry and of Physics at Queen's University in Kingston, and a Graduate Faculty Scholar in the department of physics, University of Central Florida and a Fellow of the Max-Planck-uOttawa Centre for Extreme and Quantum Photonics. In 2008, he was elected a Fellow in the American Physical Society, nominated by its Division of Chemical Physics in 2008, for contributions to ultrafast laser science as applied to molecular physics, including time-resolved studies of non-adiabatic dynamics in excited molecules, non-perturbative quantum control of molecular dynamics, and dynamics of polyatomic molecules in strong laser fields. In 2008, Stolow won the Keith Laidler Award of the Canadian Society for Chemistry, for a distinguished contribution to the field of physical chemistry, recognizing early career achievement. In 2009, he was elected a Fellow of the Optical Society of America for the application of ultrafast optical techniques to molecular dynamics and control, in particular, studies of molecules in strong laser fields and the development of new methods of optical quantum control. In 2013, he was awarded the Queen Elizabeth II Diamond Jubilee Medal (Canada). In 2017, Stolow was awarded the Earle K. Plyler Prize for Molecular Spectroscopy and Dynamics of the American Physical Society for the development of methods for probing and controlling ultrafast dynamics in polyatomic molecules, including time-resolved photoelectron spectroscopy and imaging, strong field molecular ionization, and dynamic Stark quantum control. In 2018, Stolow was awarded the John C. Polanyi Award of the Canadian Society for Chemistry “for excellence by a scientist carrying out research in Canada in physical, theoretical or computational chemistry or chemical physics”. In 2020, he became Chair of the Division of Chemical Physics of the American Physical Society. His group's research interests include ultrafast molecular dynamics and quantum control, time-resolved photoelectron spectroscopy and imaging, strong field & attosecond physics of polyatomic molecules, and coherent non-linear optical microscopy of live cells/tissues, materials and geological samples. In 2020, Stolow launched a major new high power ultrafast laser facility at the University of Ottawa producing high energy, phase-controlled few-cycle pulses of 2 micron wavelength at 10 kHz repetition rate. These are used for High Harmonic Generation to produce bright ultrafast Soft X-ray pulses for a new Ultrafast Xray Science Laboratory.
Majed Chergui is a Swiss and French physicist specialized in ultrafast dynamics of light-induced processes. He is a professor at EPFL, head of the Laboratory of Ultrafast Spectroscopy at EPFL's School of Basic Sciences, and founding director of the Lausanne Centre for Ultrafast Science (LACUS).
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