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Spectral Lines
Published in Ronald L. Snell, Stanley E. Kurtz, Jonathan M. Marr, Fundamentals of Radio Astronomy, 2019
Ronald L. Snell, Stanley E. Kurtz, Jonathan M. Marr
Oscillator strengthRadiative transitions!oscillator strength An alternative method of characterizing the probability for emission or absorption in a spectral line is using a quantity called the oscillator strength, usually denoted by f. The oscillator strength and the Einstein B coefficient for absorption are related by flu=hνmec4π2e2Blu, where me is the electron mass and e is the magnitude of the electron charge. Like the Einstein coefficients, the oscillator strengths are often tabulated for spectral transitions. Spectral lines!electronic
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
Octanol-water partition coefficient (P)* - A measure of the way in which a compound will partition itself between the octanol and water phases in the two-phase octanol-water system, and thus an indicator of certain types of biological activity. Specifically, P is the ratio of the concentration (in moles per liter) of the compound in the octanol phase to that in the water phase at infinite dilution. The quantity normally reported is log P. Oersted (Oe) - A non-SI unit of magnetic field (H), equal to 79.57747 A/m. Ohm ()* - The SI unit of electric resistance, equal to V/A. [1] Ohm's law - A relation among electric current I, potential difference V, and resistance R, viz., I = V/R. At constant temperature the resistance for many materials is constant to high precision. Olefins - Acyclic and cyclic hydrocarbons having one or more carbon-carbon double bonds, apart from the formal ones in aromatic compounds. The class olefins subsumes alkenes and cycloalkenes and the corresponding polyenes. [5] Oligomer - A substance consisting of molecules of intermediate relative molecular mass (molecular weight), the structure of which essentially comprises the multiple repetition of units derived, actually or conceptually, from molecules of low relative molecular mass. In contrast to a polymer, the properties of an oligomer can vary significantly with the removal of one or a few of its units. [8] Oligopeptides - Peptides containing from three to nine amino groups. [5] Onsager relations - An important set of equations in the thermodynamics of irreversible processes. They express the symmetry between the transport coefficients describing reciprocal processes in systems with a linear dependence of flux on driving forces. Optical rotary power - Angle by which the plane of polarization of a light beam is rotated by an optically active medium, divided by path length and by concentration of the active constituent. Depending on whether mass or molar concentration is used, the modifier "specific" or "molar" is attached. [2] Orbital - A one-electron wavefunction. Atomic orbitals are classified as s-, p-, d-, or f-orbitals according to whether the angular momentum quantum number l = 0, 1, 2, or 3. Molecular orbitals, which are usually constructed as linear combinations of atomic orbitals, describe the distribution of electrons over the entire molecule. Oscillator strength (f) - A measure of the intensity of a spectroscopic transition, defined by f= 8 2 me v 3he
A new density for transition properties within the similarity transformed equation of motion approach
Published in Molecular Physics, 2020
Soumen Ghosh, Achintya Kumar Dutta, Bernardo de Souza, Romain Berraud-Pache, Róbert Izsák
The calculation of oscillator strength requires the transition dipole , where is the excitation energy of state k. If is the dipole integral, and In other words, the transition dipole can be obtained using the density in Equation (23) or Equation (35) and substituting the left and right hand solutions corresponding to the ground state () and the kth excited state (). Since the states are different, the terms with do not contribute. With the definition of the oscillator strength, we now have all the quantities necessary to benchmark the various methods in the next section.
Photosensitivity, substituent and solvent-induced shifts in UV-visible absorption bands of naphthyl-ester liquid crystals: a comparative theoretical approach
Published in Liquid Crystals, 2014
P. Lakshmi Praveen, Durga P. Ojha
The oscillator strength is a dimensionless quantity that expresses the probability of absorption of electromagnetic radiation in transitions between energy levels of an atom or a molecule. It indicates the allowedness of electronic transitions in a molecule, and it is particularly valuable as a method of comparing ‘transition strengths’ between different types of quantum mechanical systems. A graph has been plotted between wavelength and oscillator strength (Figure 5) to understand the intensity profiles of the compounds. It may be observed from the figure that the NAPHE1 molecule exhibits the highest oscillator strength at 257.50 nm, while the NAPHE2 molecule at 240.90 nm. Further, the NAPHE1 and NAPHE2 molecules exhibit the last intensity peak around 330 nm and 320 nm, respectively. This indicates the much flexibility of the NAPHE1 molecule for electronic transitions over a long wavelength region. Further, this causes high photosensitivity for the NAPHE1 molecule, which may be exploited for electro-optic applications. The continuous decrease in absorption (Figures 3 and 4) and oscillator strength (Figure 5) clearly indicates the breakage of aromatic rings with respect to the higher wavelengths and subsequently loosing the photosensitivity. This decrease in absorption as a function of increasing UV-Vis wavelength has been consistently observed for both the molecules.
Inner-shell photoabsorption and photoionisation cross-sections of valence excited states from asymmetric-Lanczos equation-of-motion coupled cluster singles and doubles theory
Published in Molecular Physics, 2021
Torsha Moitra, Sonia Coriani, Bruno Nunes Cabral Tenorio
Total photoionisation cross-sections can be obtained by the Stieltjes Imaging procedure, suggested by Langhoff [18,19]. The cross-section is the probability for a photon of energy ω to be absorbed by a molecule and is proportional to the (differential) oscillator strength , . The oscillator strength is dimensionless.