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Selected Applications of Absorption Spectroscopy
Published in Helmut H. Telle, Ángel González Ureña, Laser Spectroscopy and Laser Imaging, 2018
Helmut H. Telle, Ángel González Ureña
Summing up all measurement uncertainties and taking into account a range of frequency corrections, the latest, revisited data evaluation yielded a frequency for the 1S−2S transition in hydrogen of ν1S–2S = 2466061413187018(11)Hz, with relative uncertainty of less than 5 × 10−15. This is by far the most precise, direct measurement of an atomic transition frequency. Such measurements are extremely valuable for the determination of fundamental entities like, e.g., the 1S-Lamb shift and the Rydberg constant; both can be derived by comparison of two transition (precisely known) frequencies in the hydrogen atom.
L
Published in Splinter Robert, Illustrated Encyclopedia of Applied and Engineering Physics, 2017
[acoustics, atomic, computational, general, mechanics, nuclear, solid-state] Physicist from the United States. Lamb was known for his work on quantum-field theory. Lamb received the Nobel Prize in Physics in 1955 for the discovery of the quantum–mechanical shift in energy levels associated with the hydrogen atom, the Lamb shift. Lamb received the Nobel Prize for his discovery of how the fine structure of hydrogen is revealing a discrepancy in the quantum theory with respect to the electron and his concept of “virtual particles” that provide an energy shift named after him as the “Lamb shift.” The concept of virtual particles can be interpreted as energy shift through the mass–energy equivalence concept. Lamb studied under Julius Robert Oppenheimer (1904–1967) and was a contemporary of Enrico Fermi (1901–1954), Isidor Isaac Rabi (1898–1988), Edward Teller (1908–2003), and John Hasbrouck Van Vleck (1899–1980), with whom he interacted. While examining the fine-structure of transitions between 2S1/2→2P1/2 and 2S1/2→2P3/2 the high resolution of 10−4GHz confirmed the Dirac predicted 2P structure (see Figure L.8).
Symbols, Terminology, and Nomenclature
Published in W. M. Haynes, David R. Lide, Thomas J. Bruno, CRC Handbook of Chemistry and Physics, 2016
W. M. Haynes, David R. Lide, Thomas J. Bruno
Kerr effect* - An electrooptical effect in which birefringence is induced in a liquid or gas when a strong electric field is applied perpendicular to the direction of an incident light beam. The Kerr constant k is given by n1-n2 = kE2, where is the wavelength, E is the electric field strength, and n1 and n2 are the indices of refraction of the ordinary and extraordinary rays, respectively. Ketenes - Compounds in which a carbonyl group is connected by a double bond to an alkylidene group: R2C=C=O. [5] Ketones - Compounds in which a carbonyl group is bonded to two carbon atoms: R1R2C=O (neither R may be H). [5] Kilogram (kg)* - The SI base unit of mass. [1] Kinetic energy (Ek, T) - The energy associated with the motion of a system of particles in a specified reference frame. For a single particle of mass m moving at velocity v, Ek = 1/2mv2. Kirchhoff's laws - Basic rules for electric circuits, which state (a) the algebraic sum of the currents at a network node is zero and (b) the algebraic sum of the voltage drops around a closed path is zero. Klein-Gordon equation - A relativistic extension of the Schrödinger equation. Klein-Nishima formula - An expression for the scattering cross section of a photon by an unbound electron, based upon the Dirac electron theory. Knight shift - The change in magnetic resonance frequency of a nucleus in a metal relative to the same nucleus in a diamagnetic solid. The effect is due to the polarization of the conduction electrons in the metal. Knudsen number (Kn) - A dimensionless quantity used in fluid mechanics, defined by Kn = /l, where is mean free path and l is length. [2] Kondo effect - A large increase in electrical resistance observed at low temperatures in certain dilute alloys of a magnetic metal in a nonmagnetic material. Kramers-Kronig relation - A set of equations relating the real and imaginary parts of the index of refraction of a medium Lactams - Cyclic amides of amino carboxylic acids, having a 1azacycloalkan-2-one structure, or analogues having unsaturation or heteroatoms replacing one or more carbon atoms of the ring. [5] Lactones - Cyclic esters of hydroxy carboxylic acids, containing a 1-oxacycloalkan-2-one structure, or analogues having unsaturation or heteroatoms replacing one or more carbon atoms of the ring. [5] Lagrangian function (L) - A function used in classical mechanics, defined as the kinetic energy minus the potential energy for a system of particles. Lamb shift - The small energy difference between the 2S1/2 and 2 P1/2 levels in the hydrogen atom, which results from interactions between the electron and the radiation field. Laminar flow - Smooth, uniform, non-turbulent flow of a gas or liquid in parallel layers, with little mixing between layers. It is characterized by small values of the Reynolds number. Landé g-factor - See g-Factor of the electron Langevin function - The mathematical function L(x) = (ex+e-x)/ (ex-e-x)-1/x, which occurs in the expression for the average dipole moment of a group of rotating polar molecules in an electric field: µav = µL(µE/kT), where µ is the electric dipole moment of a single molecule, E is the electric field strength, k is the Boltzmann constant, and T is the temperature.
Towards highly accurate calculations of parity violation in chiral molecules: relativistic coupled-cluster theory including QED-effects
Published in Molecular Physics, 2021
We are here interested in the electron self-energy (SE) and the vacuum polarisation (VP), both at the origin of the Lamb shift [64]. QED, as expressed through the scattering matrix formalism, can describe atoms and molecules to amazing precision, but is in practice limited to few-electron systems, in particular due to the slow convergence of electron correlation within this formalism [65–71]. In recent years there has been an increased interest in the use of effective QED potentials [72–75]. An early example of such a potential is the Uehling potential for vacuum polarisation [76]. The electron self-energy is more complicated to represent by a potential due to its delocal nature, but a number of such potentials are now available [77–79]. QED-effects have also been included in the fitting of relativistic effective core potentials [80,81]. We have implemented effective QED potentials in the DIRAC code for general relativistic molecular calculations [82]. A full account of our implementation will be given elsewhere [83]; very recently, a similar implementation has been reported by Skripnikov [84]. QED-effects on parity violation have previously been studied in atoms and then with focus on transition amplitudes [85–93]. We believe that the present work is the first to study radiative corrections to molecular PV energies.