Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “RED SHIFT”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1966

Doppler interpretation of quasar red shifts.

Quasi-stellar sources as local objects moving with velocities close to speed of light, noting transverse Doppler effect leads to expectation of fewer blue shifts than red shifts

DOPPLER EFFECT↗
DOE OSTI2019

Crystal Chemistry, Band-Gap Red Shift, and Electrocatalytic Activity of Iron-Doped Gallium Oxide Ceramics

This work for the first time unfurls the fundamental mechanisms and set the stage for an approach to derive electrocatalytic activity, which is otherwise not possible, in a traditionally known wide band gap oxide material. Specifically, we report on the tunable optical properties, in terms of wide spectral selectivity and red-shifted band gap, and electrocatalytic behavior of iron (Fe) doped gallium oxide (ß-Ga 2 O 3 ) model system. X-ray diffraction (XRD) studies of sintered Ga 2-x Fe x O 3 (GFO) (0.0 ≤ x ≤ 0.3) compounds provide evidence for the Fe 3+ substitution at Ga 3+ site without any secondary phase formation. Rietveld refinement of XRD patterns reveal that the GFO compounds crystallize in monoclinic crystal symmetry with C2/m space group. The electronic structure of the GFO compounds probed using X-ray photoelectron spectroscopy data reveals that, at lower concentrations of Fe exhibits mixed chemical valence states (Fe 3+ , Fe 2+ ), whereas single chemical valence state (Fe 3+ ) is evident for higher Fe content (x = 0.20-0.30). The optical absorption spectra reveal a significant red shift in the optical band gap with Fe doping. The origin of the significant red shift even at low concentrations of Fe (x = 0.05) is attributed to the strong sp-d exchange interaction originated from the 3 d 5 electrons of Fe 3+ . The optical absorption edge observed at ˜450 nm with lower intensity is the characteristic of Fe doped compounds associated with Fe 3+ - Fe 3+ double excitation process. Coupled with optical band gap red shift, electrocatalytic studies of GFO compounds reveals that, interestingly, Fe doped Ga 2 O 3 compound exhibits electrocatalytic activity in contrast to intrinsic Ga 2 O 3 . Fe doped samples (GFO) demonstrated appreciable electrocatalytic activity towards the generation of H 2 through electrocatalytic water splitting. An onset potential and tafel slope of GFO compounds includes: ~900 mV, ~210 mVdec -1 (x = 0.15) and ~1036 mV, ~290 mVdec-1 (x = 0.30). The electrocatalytic activity of Fe doped Ga-oxide compounds is attributed to cumulative effect of different mechanisms such as; doping resulted new catalytic centers, enhanced conductivity and electron mobility. Hence, in this report, for the first time, we explored a new pathway; electrocatalytic behavior of Fe doped Ga 2 O 3 resulted due to Fe chemical states, red shift in optical band gap. The implications derived from this work may be applicable to a large class of compounds and further options may be available to design functional materials for electrocatalytic energy production.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1973

The second-order gravitational red shift

The direct measurement of the nonlinear term of the gravitational field equations by using very stable clocks is discussed along with measuring the perhelion advance of a planet or satellite. These are considered measurements of the second-order gravitational red shift. The exact expression for the frequency shift of light in a gravitational field is derived. Other topics discussed include: The Doppler-cancelling technique; the second-order red shift in a spherically symmetric gravitational field; finite signal transit time; and the reality and interpretation of coordinates in the second-order red shift experiment.

Jaffe, J.↗
NASA NTRS1990

A tentative explanation of cosmological red shift

The authors suggest a possible alternative explanation of cosmological red shift. They consider that there exists a background field in the universe, and that light (the photon) has an extremely weak interaction with this background, and as result, experiences an energy loss. By analogy with damped oscillations, the authors introduce a dumping term with the first derivative with respect to time in the wave equation. The solution yields a linearly reduced frequency of the light with travel distance. The purpose of this exercise is to demonstrate how a simple alternative interpretation of the Hubble relation can be generated.

Chang, T.↗
DOE OSTI2015

Infrared Multiphoton Dissociation Spectroscopy of a Gas-Phase Complex of Uranyl and 3-Oxa-Glutaramide: An Extreme Red-Shift of the [O=U=O]²⁺ Asymmetric Stretch

The gas-phase complex UO₂(TMOGA)₂²⁺ (TMOGA = tetramethyl-3-oxa-glutaramide) prepared by electrospray ionization was characterized by infrared multiphoton dissociation (IRMPD) spectroscopy. The IRMPD spectrum from 700–1800 cm⁻¹ was interpreted using a computational study based on density functional theory. The predicted vibrational frequencies are in good agreement with the measured values, with an average deviation of only 8 cm⁻¹ (<1%) and a maximum deviation of 21 cm⁻¹ (<2%). The only IR peak assigned to the linear uranyl moiety was the asymmetric ν₃ mode, which appeared at 965 cm⁻¹ and was predicted by DFT as 953 cm⁻¹. This ν₃ frequency is red-shifted relative to bare uranyl, UO₂²⁺, by ca. 150 cm⁻¹ due to electron donation from the TMOGA ligands. Based on the degree of red-shifting, it is inferred that two TMOGA oxygen-donor ligands have a greater effective gas basicity than the four monodentate acetone ligands in UO₂(acetone)₄²⁺. The uranyl ν₃ frequency was also computed for uranyl coordinated by two TMGA ligands, in which the central Oether of TMOGA has been replaced by CH₂. The computed ν₃ for UO₂(TMGA)₂²⁺, 950 cm⁻¹, is essentially the same as that for UO₂(TMOGA)₂²⁺, suggesting that electron donation to uranyl from the Oether of TMOGA is minor. The computed ν₃ asymmetric stretching frequencies for the three actinyl complexes, UO₂(TMOGA)₂²⁺, NpO₂(TMOGA)₂²⁺ and PuO₂(TMOGA)₂²⁺, are comparable. This similarity is discussed in the context of the relationship between ν₃ and intrinsic actinide-oxygen bond energies in actinyl complexes.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2019

Red-Shifted Absorptions of Cation-Defective and Surface-Functionalized Anatase with Enhanced Photoelectrochemical Properties

Manipulating the atomic structure of semiconductors is a fine way to tune their properties. The rationalization of their modified properties is, however, particularly challenging as defects locally disrupt the long-range structural ordering, and a deeper effort is required to fully describe their structure. In this work, we investigated the photoelectrochemical properties of an anatase-type structure featuring a high content of titanium vacancies stabilized by dual-oxide substitution by fluoride and hydroxide anions. Such atomic modification induces a slight red-shift band gap energy of 0.08 eV as compared to pure TiO 2 , which was assigned to changes in titanium–anion ionocovalent bonding. Under illumination, electron paramagnetic resonance spectroscopy revealed the formation of Ti III and O 2 – radicals which were not detected in defect-free TiO 2 . Consequently, the modified anatase shows higher ability to oxidize water with lower electron–hole recombination rate. To further increase the photoelectrochemical properties, we subsequently modified the compound by a surface functionalization with N-methyl-2-pyrrolidone (NMP). This treatment further modifies the chemical composition, which results in a red shift of the band gap energy to 3.03 eV. Moreover, the interaction of the NMP electron-donating molecules with the surface induces an absorption band in the visible region with an estimated band gap energy of 2.25–2.50 eV. Under illumination, the resulting core–shell structure produces a high concentration of reduced Ti III and O 2 – , suggesting an effective charge carrier separation which is confirmed by high photoelectrochemical properties. This work provides new opportunities to better understand the structural features that affect the photogenerated charge carriers.

74 ATOMIC AND MOLECULAR PHYSICS↗
NASA NTRS1993

GRO: Red-shifted electron-positron annihilation gamma-rays from radiopulsars

Reported red-shifted e(+) + e(-) yields gamma + gamma 511 keV gamma-rays from the Crab pulsar would, if ultimately confirmed, provide crucial clues about the structure of the powerful magnetospheric accelerator in that rapidly spinning gamma-ray pulsar. In an attempt to understand the origin of this component of the Crab pulsar's emission, we try to account for the following: (1) a flow of approximately 10 exp 40 e(+/-)/s into near the surface of the neutron star; (2) a relatively narrow annihilation line implying that the annihilating e(+/-) pairs probably had a velocity (along vector B) less than or approximately = 10(exp -1)c; and (3) a tentative light curve suggesting a doubly peaked structure different from that of the rest of the Crab pulsar's nonthermal radiation.

Ruderman, Malvin↗