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Results for “ELECTRON TRANSITION”

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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

Electronic transition moment for the B(2)II-X(2)II system of NO

The upsilon' = 0-3 and 7 vibrational levels of the NO B(2)II state have been selectively excited by laser radiation. The fluorescence spectra together with calculated Franck-Condon factors and r-centroids have been used to evaluate the electronic transition moment. The results for upsilon' = 0-3 are in very good agreement with recent chemiluminescence measurements and ab initio calculations. Furthermore, the data from upsilon' = 7 have been used to extend the empirically determined moment to limits 1.23 and 1.78 A, improving agreement with experimentally determined lifetimes.

Luque, Jorge↗
DOE OSTI2023

Effect of electronic transitions on near edge optical properties of off-stoichiometric boron carbide thin films

In the present study, soft x-ray optical properties of off-stoichiometric boron carbide thin films are investigated, and the structure and chemical composition of the film is analyzed using angle dependent x-ray reflectivity and x-ray photoelectron spectroscopy techniques. Energy dependent soft x-ray reflectivity measured at a fixed grazing angle of 1.5° is used to determine the optical constants in the boron K edge region by applying the Kramers–Kronig technique. The measured optical constants show near edge fine features corresponding to σ* and π* resonances. Furthermore, the electronic transitions corresponding to σ* resonance cause a 40%–75% increase in the delta value in the above boron K edge region. The π* transitions corresponding to off-stoichiometric nature of the boron carbide are observed in the absorption spectra near ~ 192.7 eV. Details of the measured soft x-ray optical properties of the off-stoichiometric boron carbide thin film are discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2024

La 0.6 Sr 0.4 CoO 3−δ Films Under Deoxygenation: Magnetic And Electronic Transitions Are Apart from The Structural Phase Transition

Abstract Topotactic phase transitions induced by changes in the oxygen vacancy concentration can largely alter the physical properties of complex oxides, including electronic and magnetic phases, while maintaining the structural integrity of the crystal lattice. An oxygen‐vacancy‐induced topotactic phase transition from perovskite (PV) to brownmillerite (BM) is achieved in epitaxial La 0.6 Sr 0.4 CoO 3−δ (LSCO) thin films. Two novel intermediate states with different oxygen content are identified by X‐ray diffraction, which involves a single‐phase reduced PV state and a mixed state of co‐existing PV and BM. The combination of depth‐sensitive polarized neutron reflectometry (PNR) and Rutherford backscattering (RBS) allows a quantitative determination of magnetization and the mean oxygen content in all states, revealing a continuous transition from La 0.6 Sr 0.4 CoO 2.97 to La 0.6 Sr 0.4 CoO 2.5 . BM formation is observed for an LSCO layer with an oxygen content of 2.67, while the magnetic and electronic transition already occurs for a layer with a higher oxygen content of 2.77 (and above) and in the absence of a BM signature. These results demonstrate that the physics of electronic metal‐to‐insulator transition (MIT), magnetic ferromagnet‐to‐non‐ferromagnet transition (FM‐to‐non‐FM), and structural PV‐to‐BM phase transition should be considered within the framework of separate but interrelated processes.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Isostructural electronic transition in MoS 2 probed by solid-state high-harmonic generation spectroscopy

Studying materials under extreme pressure in diamond anvil cells (DACs) is key to discovering emergent states of matter, yet no method currently allows the direct measurement of the electronic structure in this environment. Solid-state high-harmonic generation (sHHG) offers a unique all-optical window into the electronic structure of materials. We demonstrate sHHG spectroscopy inside a DAC by probing 2H-MoS 2 , up to 30 GPa, revealing a pressure-induced crossover of the lowest direct bandgap from the K-point to the Γ-point. This transition manifests as a sharp minimum in harmonic intensity and a 30° rotation of the sHHG polarization anisotropy, despite the absence of a structural phase change. First-principles simulations attribute these features to interference between competing excitation pathways at distinct points in the Brillouin zone. Our results establish sHHG as a sensitive probe of electronic transitions at high pressure, enabling access to quantum phenomena that evade detection by conventional techniques.

Nebgen, Bailey R. [University of California, Berke↗
NASA NTRS1976

Electronic transition CN laser

A 20 kW electric-discharge pumped CN laser oscillating on the A(2) Pi-X(2) Sigma molecular system is presented. Excitation is by a simple longitudinal discharge struck through HCN vapor. Twenty kW peak power is generated in a 150 nsec full-width half-maximum pulse. Two lasing bands were observed in the A-X system: the (0,1) and (0,2) bands near 1.42 and 2.0 microns respectively. Both P and Q branches are active in the two bands, with Q bands stronger. Peak laser energy is 3 mJ. Products of UV photolysis of HCN, electron impact excitation of HCN, and other possible excitation mechanisms and laser efficiency are discussed.

Quick, C. R., Jr.↗
DOE OSTI2024

Searching for Muon to Electron Transition [Slides]

Summary : Searches for violations of fundamental symmetries and conservation laws - Powerful Probes of physics beyond the Standard Model (BSM); Charged Lepton Flavor violation : Mu to E conversion; 4-orders of magnitude improvements in BR; SD process can dominate the conversion process in ALP models; fa > O(100)TeV can be achieved, complementary role.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1976

Nuclear fission fragment excitation of electronic transition laser media

Specific characteristics of the media including density, excitation rates, wavelength, kinetics, fissile material, scale size, and medium uniformity are assessed. The use of epithermal neutrons, homogeneously mixed fissile material, and special high cross section nuclear isotopes to optimize coupling of the energy to the medium are shown to be important considerations maximizing the scale size, energy deposition, and medium uniformity. It is demonstrated that e-beam excitation can be used to simulate nuclear pumping conditions to facilitate the search for candidate media.

Lorents, D. C.↗
NASA NTRS1978

A theoretical study of the electronic transition moment for the C2 Swan band system

Large-scale self-consistent-field plus configuration-interaction calculations have been performed for the a 3Pi u and d 3Pi g states of C2. The theoretical potential curves are in good agreement with those found by a Klein-Dunham analysis of measured molecular constants in terms of shape and excitation energy. The sum of the squares of the theoretical transition moments between the states at 2.44 bohr is 4.12 a.u. which agrees with the results of shock tube measurements. The variation in the sum of the squares of the theoretical moments with internuclear separation agrees with the values of Danylewych and Nicholls (1974). Based on the data for C2 and mother molecules, it is suggested that CI calculations using near Hartree-Fock quality Slater basis sets produce highly reliable transition moments.

Arnold, J. O.↗
NASA NTRS1979

Nuclear pumped electronic transition laser studies

An experiment is proposed that should yield unambiguous absolute results on the production efficiency of rare gas excimers from fission fragments. Laser threshold efficiency is parameterized and calculations indicate that some lasers can be operated using relatively simple experimental apparatus adjacent to GODIVA. Operation of a KrF excimer laser adjacent to GODIVA appears to be possible, although the neutron pulse width is not well matched to the laser pulse duration. However, calculation indicates that KrF excimer laser output on the order of a joule may be possible.

Hughes, W. M.↗