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Quantum Physics Of Atoms, Molecules, Solids, Nu...
The photoelectric effect is the emission of electrons when electromagnetic radiation, such as light, hits a material. Electrons emitted in this manner are called photoelectrons. The phenomenon is studied in condensed matter physics, and solid state and quantum chemistry to draw inferences about the properties of atoms, molecules and solids. The effect has found use in electronic devices specialized for light detection and precisely timed electron emission.
Quantum Physics of Atoms, Molecules, Solids, Nu...
Because the kinetic energy of the emitted electrons is exactly the energy of the incident photon minus the energy of the electron's binding within an atom, molecule or solid, the binding energy can be determined by shining a monochromatic X-ray or UV light of a known energy and measuring the kinetic energies of the photoelectrons.[17] The distribution of electron energies is valuable for studying quantum properties of these systems. It can also be used to determine the elemental composition of the samples. For solids, the kinetic energy and emission angle distribution of the photoelectrons is measured for the complete determination of the electronic band structure in terms of the allowed binding energies and momenta of the electrons. Modern instruments for angle-resolved photoemission spectroscopy are capable of measuring these quantities with a precision better than 1 meV and 0.1.
Both subfields are primarily concerned with electronic structure and the dynamical processes by which these arrangements change. Generally this work involves using quantum mechanics. For molecular physics, this approach is known as quantum chemistry. One important aspect of molecular physics is that the essential atomic orbital theory in the field of atomic physics expands to the molecular orbital theory.[5] Molecular physics is concerned with atomic processes in molecules, but it is additionally concerned with effects due to the molecular structure. Additionally to the electronic excitation states which are known from atoms, molecules are able to rotate and to vibrate. These rotations and vibrations are quantized; there are discrete energy levels. The smallest energy differences exist between different rotational states, therefore pure rotational spectra are in the far infrared region (about 30 - 150 µm wavelength) of the electromagnetic spectrum. Vibrational spectra are in the near infrared (about 1 - 5 µm) and spectra resulting from electronic transitions are mostly in the visible and ultraviolet regions. From measuring rotational and vibrational spectra properties of molecules like the distance between the nuclei can be calculated.[6]
Researchers in optical physics use and develop light sources that span the electromagnetic spectrum from microwaves to X-rays. The field includes the generation and detection of light, linear and nonlinear optical processes, and spectroscopy. Lasers and laser spectroscopy have transformed optical science. Major study in optical physics is also devoted to quantum optics and coherence, and to femtosecond optics.[1] In optical physics, support is also provided in areas such as the nonlinear response of isolated atoms to intense, ultra-short electromagnetic fields, the atom-cavity interaction at high fields, and quantum properties of the electromagnetic field.[11]
Over the past 20 years, nanotechnology has been a booming area of research in chemistry, biology, physics, engineering, and medicine. Modern techniques have allowed scientists to better study small materials, and the nanotech we read about in science fiction novels can now become real products found in our world. In this seminar, we will discuss what is so special about the size range of 1-100 nm (the nanoscale) and why particles of this size have such a unique niche in nature and technology. We will explore the properties of these materials and why quantum mechanical effects allow for this scale to be so important. Discussions of medicines, electronics, catalysts, additives, and imaging agents that include nanoparticles will allow us to explore the wide range of current directions of nanotechnology. As we look to future applications, we will debate the implications of these materials on the environment, human health, and safety. Regulatory bodies in the United States and around the globe have discussed the ethical and social impact of nanomaterials, and we will investigate their role is assuring the nanomaterials we use leave a positive impact on the world.
This class is a chemistry class designed for non-scientists. Students will look at atoms, molecules, and compounds, but not with the rigorous treatment that is found in a typical chemistry course. We will avoid the physics and math that are employed in a typical chemistry class. By reading about and researching various chemistry topics, students will come to appreciate the presence and importance of chemistry in every aspect of day-to-day life.Students in this course may not have taken General Chemistry or Organic Chemistry at Northwestern unless by department permission (please contact chemhelp@northwestern.edu to request permission).
This course is an introduction to quantum mechanics and includes applications in spectroscopy. Topics to be covered include: The wave equation (the transition from classical to quantum mechanics), the Schrodinger equation, particle-in-a-box models, QM operators, the postulates of QM, the harmonic oscillator and rigid rotor, the hydrogen atom, multi-electron atoms, and approximate methods for solving the Schrodinger equation.
Accurate spectroscopy of simple calculable atomic and molecular systems has proven its importance for studying fundamental physics and testing quantum theory. A particularly important role has been played by atomic hydrogen. In addition to its large contribution to the development and tests of quantum electrodynamics, accurate spectroscopy of atomic hydrogen provides the energy scale for ab initio quantum calculations (the Rydberg constant) and gives an important contribution to the global adjustment of fundamental constants1. Several other calculable systems, such as helium atom2,3, HD+ ion4,5, exotic atoms6,7,8 or hydrogen molecule, contribute to testing quantum theory, determining fundamental constants and searching for new physics beyond the standard model9,10,11. When considering a long-term perspective, H2 possesses a huge advantage over other system, which is a set of a few hundred ultralong (a week) living rovibrational states12. The ratio of the natural linewidth to the optical transition frequency is on the order of \(10^-20\) which, for a typical ability of resolving a \(10^-4\) fraction of the linewidth, gives the ultimate limit on testing fundamental physics with H2 at \(10^-24\) relative accuracy.
Quantum mechanics had initially the aim to explain the line spectra of atoms seen in optical spectroscopy. The first successful attempt was the Bohr model based on seemingly "ad hoc" postulates. These postulates are actually consequences of the elegant mathematical treatment of the Coulomb problem based on first principles of quantum mechanics. The appearance of angular momentum in this special case hints to its significance in quantum physics.
These postulates cannot be understood on the basis of classical physics. An electron moving around the nucleus has a centripetal acceleration, and as all accelerating electric charges it is expected to radiate and lose energy. This would eventually let it fall into the nucleus, so the atom could not be a stable object, which is in sharp contradiction with observations. Therefore the postulates seemed to be "ad hoc". Still they were highly significant, because these statements turned out to be true in view of the "true" quantum mechanics, as well. In that theory, however, these are not fundamental statements but consequences of the deeper general principles and formalism of quantum mechanics.
British-born John Pople was a pioneer in the theoretical study of the properties of molecules. His research focused on applying the complicated mathematics of quantum mechanics to study the chemical bonding between atoms within molecules. In 1970, the first version of the Pople-designed Gaussian computer program was published. It made his computational techniques easily accessible to chemists in universities and commercial enterprises throughout the world. Pople won the 1998 Nobel Prize in Chemistry, sharing the honor with Walter Kohn of the University of California, Santa Barbara, whose research is similar to Pople's but is more focused on the properties of solid materials, such as metals. Pople was rewarded, in the words of the Nobel Prize Committee, "for developing computational methods making possible the theoretical study of molecules, their properties and how they act together in chemical reactions. These methods are based on the fundamental laws of quantum mechanics."
Prof. Atatüre is the scientific lead of the Quantum Optical Materials and Systems (QOMS) team at the University of Cambridge. His current research efforts include optical control of spin-photon interfaces in solids, development of nanoscale quantum sensors and investigations of novel quantum materials and devices. He is also a co-founder and CSO of QOMS quantum-tech spin out, Nu Quantum Ltd. Furthermore, he dedicates significant time to science communication and public engagement on the role of science in society, scientific integrity, and achieving diversity and equality in science. He held more than 200 plenary, keynote and invited talks, colloquia and departmental seminars, as well as three TEDx Talks on the topics of quantum physics, light, and science and diversity. 041b061a72