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Results for “spin-orbit coupling”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Photodetachment of an electron from selenide ion - The electron affinity and spin-orbit coupling constant for SeH.

The relative cross section for the gas phase photodetachment of an electron from SeH(-) was determined in the wavelength region 428 to 578 nm. An ion cyclotron resonance spectrometer was used to generate, trap, and detect the negative ions, and a 1000-W xenon arc lamp with a grating monochromator was employed as the light source. The cross section exhibited two sharp thresholds, whose positions remained unchanged for the photodetachment of SeD(-). As a result of these thresholds, the electron affinity and the spin-orbit coupling constant were evaluated.

Smyth, K. C.↗
NASA NTRS1973

Bombardment as a cause of the lunar asymmetry.

The moon is asymmetric in crustal thickness and also in the distribution of maria and gamma radioactivity. Early bombardment of the moon by planetesimals, in both heliocentric and geocentric orbits, is examined as a possible cause of the asymmetries. The presence of a massive companion (earth) causes a spin-orbit coupled moon to be bombarded nonuniformly. The most pronounced local concentration of impacts would have occurred on the west limb of the moon, when it orbited close to the earth, if low-eccentricity heliocentric planetesimals were still abundant in the solar system at that time. A very intense bombardment of this type could have redistributed crustal material on the moon, thinning the west limb crust appreciably. This would have caused a change in position of the principal axes of inertia, and a reorientation of the spin-orbit coupled moon such that the thinnest portion of its crust turned toward one of the poles. Erupting lavas would have preferentially flooded such a thin-crusted, low-lying area. This would have caused another readjustment of principal moments, and a reorientation of the moon such that the mare areas tipped toward the equator.

Wood, J. A.↗
NASA NTRS1971

Transition moments, Franck-Condon factors, and lifetimes of forbidden transitions - Calculation of the intensity of the Cameron system of CO.

Discussion of the factors affecting the intensity of forbidden transitions in diatomic molecules. It is shown that using Franck-Condon factors to predict relative band intensities is less reliable for forbidden transitions than it is for allowed transitions. The intensity of the 0,0 and 1,0 bands of the a super 3 pi-super 1 sigma Cameron system of CO are calculated using perturbation theory. The intensity arises from spin-orbit mixing of the A super 1 pi state with the a super 3 pi state. From the known spin-orbit coupling constant of the a super 1 pi state and the known intensity of the fourth positive A super 1 pi-super 1 sigma transition, the oscillator strengths of the 0,0 and 1,0 bands are calculated to be 1.63 x 10 to the minus 7th power and 1.99 x 10 to the minus 7th power. Lifetimes of various rotational levels are shown to range from 2.9 to several hundred milliseconds.-

James, T. C.↗
NASA NTRS1972

Angular dependence of electron impact excitation cross sections of O2.

Study of the electron-impact excitation spectrum of O2 at 20 and 45 eV impact energies and at scattering angles ranging from 10 to 90 deg. The angular behavior of the differential scattering cross sections for excitation of the a super 1 delta sub g, b super 1 sigma sub g (+), B super 3 sigma sub u (-) states for the 9.97-eV ('longest' band) and the 10.29-eV ('second' band) transitions, for the broad feature at 6.1 eV energy-loss, and for elastic scattering is determined. The experimentally measured relative differential and integral cross sections for these processes are approximately normalized to the absolute scale. The intensities of the different transitions in optical and electron-impact spectra are compared, and the importance of spin-orbit coupling and exchange processes is discussed. It is found that the energy-loss feature at 6.1 eV in the electron-impact spectrum is mostly due to the excitation of the c super 1 sigma sub u (-) state, and not the A super 3 sigma sub u (+) state, as had been previously thought.

Trajmar, S.↗
NASA NTRS1973

Rotation of solid bodies in the solar system

The effects of elastic distortion, nonprincipal axis rotation, precessing orbits, and internal dissipation on the rotation of a solid solar system body, which is in the gravitational field of an exterior body, are relatively easily analyzed by a Hamiltonian theory developed here. Examples of applications include the Chandler wobble, wobble of the moon, spin-orbit coupling, generalized Cassini laws, and tidal evolution.

Peale, S. J.↗
NASA NTRS1976

Electronic states of Zn2 - Ab initio calculations of a prototype for Hg2

The electronic states of Zn2 are investigated by ab initio polarization configuration-interaction calculations. Molecular states dissociating to Zn(1S) + Zn(1S, 3P, 1P) and Zn(3P) + Zn(3P) are treated. Important effects from states arising from Zn(+)(25) + Zn(-)(2P) are found in the potential-energy curves and electronic-transition moments. A model calculation for Hg2 based on the Zn2 curves and including spin-orbit coupling leads to a new interpretation of the emission bands in Hg vapor.

Hay, P. J.↗
NASA NTRS1977

Flight to Mercury

The project development and active flight of the Mariner 10 deep-space probe mission is recounted in detail, with sequential blow-by-blow coverage. Early studies and speculation on the planet Mercury are reviewed, and the spin-orbit coupling and near-synchronous rotation of the planet are described. Use of Venus as a slingshot in a gravity-assist maneuver is described, and Mariner 10 records of Venus are shown. The three encounters of Mariner 10 with Mercury (March 1974, Aug. 1974, March 1975) are described in detail, with purposes, problems, mishaps, and glossy photographs recovered from Mariner 10 data. Information on the planet's magnetosphere, surface topography, inferred internal structure, and IR signature is provided, and the end-of-mission improvised solar-sail experiment is outlined.

Murray, B.↗
NASA NTRS1979

Ab initio studies of the electronic structure of UF6, UF6/+/, and UF6/-/ using relativistic effective core potentials

The paper presents ab initio calculations performed on the electronic states of UF6, UF6(+), and UF6(-) using a relativistic effective core potential (ECP) for uranium and a nonrelativistic ECP for fluorine. In most of the calculations 56 valence electrons are treated explicitly using a contracted (3s 3p 2d 2f/2s2p) Gaussian basis. It is noted that various ECP's were explored, but all yield an overall charge density of U(+2.4)/F(-0.4)/6. In addition, the bonding in the ground state of UF6 is discussed. SCF and CI calculations on UF6(+) are compared with the experimental photoelectron spectrum and with previous scattered wave calculations. Further, the role of spin-orbit coupling in the states of UF6(+) and UF6(-) is covered. Finally, it is concluded that the calculated electron affinity of UF6 (7.1 eV) is considerably larger than in current experimental estimates, but the relative energies of the states of UF6(-) are in agreement (0.1-0.2 eV) with those of the experiment.

Hay, P. J.↗
NASA NTRS1977

Quantum mechanical theory of a structured atom-diatom collision system - A + BC/1-Sigma/

The problem of a 2-p state atom colliding with a singlet sigma state diatom, which involves multiple potential surfaces, is investigated. Within a diabatic representation for the electronic degrees of freedom (plus spin-orbit interaction), coupled scattering equations are derived in both space-fixed and body-fixed coordinate systems. Coefficients, analogous to Percival-Seaton coefficients, are obtained. Approximations to the exact equations, including angular momenta decoupling approximations, are discussed for both the space-fixed and body-fixed formalisms.

Devries, P. L.↗
NASA NTRS1978

Quantum-mechanical theory including angular momenta analysis of atom-atom collisions in a laser field

The problem of two atoms colliding in the presence of an intense radiation field, such as that of a laser, is investigated. The radiation field, which couples states of different electronic symmetry, is described by the number state representation while the electronic degrees of freedom (plus spin-orbit interaction) are discussed in terms of a diabatic representation. The total angular momentum of the field-free system and the angular momentum transferred by absorption (or emission) of a photon are explicitly considered in the derivation of the coupled scattering equations. A model calculation is discussed for the Xe + F collision system.

Devries, P. L.↗
NASA NTRS1977

Comment on the relation between the nonadiabatic coupling and the complex intersection of potential energy curves

Simple relations are discussed that provide a correspondence between the complex intersection of two potential surfaces and the nonadiabatic coupling matrix element between those surfaces. These are key quantities in semiclassical and quantum-mechanical theories of collision-induced electronic transitions. Within the two-state approximation, the complex intersection is shown to be directly related to the location and magnitude of the peak in the nonadiabatic coupling. Two cases have been considered: (1) the avoided crossing between two potential surfaces, and (2) the spin-orbit interaction due to a 2P halogen atom. Comparisons are made between the results of the two-state model and the results of ab initio quantum chemical calculations.

Jaffe, R. L.↗
NASA NTRS1979

Quantum-mechanical calculation of three-dimensional atom-diatom collisions in the presence of intense laser radiation

A formalism is presented for describing the collision of fluorine with the hydrogen molecule in the presence of intense radiation. For a laser frequency on the order of the spin-orbit splitting of fluorine, the interaction of the molecular system with the radiation occurs at relatively long range where, for this system, the electric dipole is vanishingly small. Hence the interaction occurs due to the magnetic dipole coupling. Even so, at low collision energies a substantial enhancement of the quenching cross section is found for a radiation intensity of 10 to the 11th W/sq cm.

Devries, P. L.↗
NASA NTRS1977

A spin-orbit constraint on the viscosity of a Mercurian liquid core

The escape of Mercury from the stable spin-orbit resonance in which the spin angular velocity is twice the orbital mean motion (2n) requires that the kinematic viscosity of a molten core with a laminar boundary layer be comparable to that of water (0.01 sq cm/s) and the tidal Q be less than about 100. If the boundary layer is turbulent, escape from the resonance is only consistent with a liquid core of low viscosity if the critical Reynolds number for the onset of turbulence is above about 500, the moment difference (B - A)/C is below about 0.00001, and the tidal dissipation factor Q is less than about 40. These conclusions depend on the assumptions that Mercury's obliquity was near 0 deg at the time of resonance passage, that the liquid core was not stably stratified at the time at which Mercury passed through the resonance, that a turbulent boundary layer can be characterized by a turbulent or eddy viscosity coefficient, and that the most important coupling between core and mantle is a viscous coupling at a smooth spherical boundary.

Peale, S. J.↗