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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 1,081 records · Page 60
All sourcesNASA NTRSDOE OSTI
DOE OSTI2010

Ultrashort-pulse-train pump and dump excitation of a diatomic molecule

An excitation scheme is proposed for transferring population between ground-vibrational levels of a molecule. The transfer is accomplished by pumping and dumping population with a pair of coherent ultrashort-pulse trains via a stationary state. By mismatching the teeth of the frequency combs associated with the pulse trains to the vibrational levels, high selectivity in the excitation, along with high transfer efficiency, is predicted. The pump-dump scheme does not suffer from spontaneous emission losses, it is insensitive to the pump-dump-train delay, and it requires only basic pulse shaping.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2011

Laser cooling of the vibrational motion of Na{sub 2} combining the effects of zero-width resonances and exceptional points

We propose various scenarios for molecular vibrational cooling combining the effects of two kinds of resonance states occurring during the photodissociation of Na{sub 2} taken as an illustrative example. Such resonances result from an appropriate sampling of laser parameters (wavelength and intensity): (a) For particular choices of intensity and wavelength, two resonance energies can be brought to complete coalescence, with their positions and widths becoming equal and leading to a so-called exceptional point (EP) in the parameter plane. Advantage can be taken from such points for very selective laser-controlled vibrational transfer strategies. (b) For specific intensities, far beyond the perturbation regime, some resonances can have a zero width (infinite lifetime). They are referred to as a zero-width resonance (ZWR) and may be used for vibrational purification purposes. We show how appropriately shaped, experimentally reachable laser pulses, encircling EPs or inducing ZWRs, may be used for a thorough and comprehensive control aiming at population transfer or purification schemes, which, starting from an initial field-free vibrational distribution, ends up in the ground vibrational level.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

Effect of thermochemical treatments on laser-induced luminescence spectra from strontium titanate: comparison with swift ion-beam irradiation experiments

Results recently reported on the effect of thermochemical treatments on the (He-Cd) laser-excited emission spectra of strontium titanate (STO) are re-analyzed here and compared with results obtained under ion-beam irradiation. Contributing bands centered at 2.4 eV and 2.8 eV, which appear under laser excitation, present intensities dependent upon previous thermal treatments in oxidizing (O 2 ) or reducing atmosphere (H 2 ). As a key result, the emission band centered at 2.8 eV is clearly enhanced in samples exposed to a reducing atmosphere. From a comparison with the ionoluminescence data, it is concluded that the laser-excited experiments can be rationalized within a framework developed from ion-beam excitation studies. In particular, the band at 2.8 eV, sometimes attributed to oxygen vacancies, behaves as expected for optical transitions from conduction-band (CB) states to the ground state level of the self-trapped exciton center. The band at 2.0 eV reported in ion-beam irradiated STO, and attributed to oxygen vacancies, is not observed in laser-excited crystals. As a consequence of our analysis, a consistent scheme of electronic energy levels and optical transitions can now be reliably offered for strontium titanate.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2017

Tropospheric Ozone Assessment Report: Database and Metrics Data of Global Surface Ozone Observations

In support of the first Tropospheric Ozone Assessment Report (TOAR) a relational database of global surface ozone observations has been developed and populated with hourly measurement data and enhanced metadata. A comprehensive suite of ozone data products including standard statistics, health and vegetation impact metrics, and trend information, are made available through a common data portal and a web interface. These data form the basis of the TOAR analyses focusing on human health, vegetation, and climate relevant ozone issues, which are part of this special feature. Cooperation among many data centers and individual researchers worldwide made it possible to build the world's largest collection of in-situ hourly surface ozone data covering the period from 1970 to 2015. By combining the data from almost 10,000 measurement sites around the world with global metadata information, new analyses of surface ozone have become possible, such as the first globally consistent characterisations of measurement sites as either urban or rural/remote. Exploitation of these global metadata allows for new insights into the global distribution, and seasonal and long-term changes of tropospheric ozone and they enable TOAR to perform the first, globally consistent analysis of present-day ozone concentrations and recent ozone changes with relevance to health, agriculture, and climate. Considerable effort was made to harmonize and synthesize data formats and metadata information from various networks and individual data submissions. Extensive quality control was applied to identify questionable and erroneous data, including changes in apparent instrument offsets or calibrations. Such data were excluded from TOAR data products. Limitations of a posteriori data quality assurance are discussed. As a result of the work presented here, global coverage of surface ozone data for scientific analysis has been significantly extended. Yet, large gaps remain in the surface observation network both in terms of regions without monitoring, and in terms of regions that have monitoring programs but no public access to the data archive. Therefore future improvements to the database will require not only improved data harmonization, but also expanded data sharing and increased monitoring in data-sparse regions.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

AmeriFlux MX-PMm Puerto Morelos mangrove

This is the AmeriFlux version of the carbon flux data for the site MX-PMm Puerto Morelos mangrove. Site Description - The tower was located at the “Dr. Alfredo Barrera Marín” Botanical Garden. The surface monitored is covered with basin mangrove (sporadically flooded wetland) that grows in a fringe parallel to the northeastern coast (ca. 1 km) of the Yucatan Peninsula. The dominant species are Rhizophora mangle and Conocarpus erectus, which grow intertwined and relatively stunted (max tree height is 5m). Under the influence of trade winds and frequent stroms. The vegetation is regenerating after complete defoliation due to hurricane Wilma (cat. 4) passing in October 2005. The site is sporadically flooded by rainfall soil saturation excess; there are no marine surface water inputs but ground water level fluctuations show tidal signals. The terrain of the monitored surface is flat, while the area downwind of the tower presents a slope which corresponds to an ancient coast line. There is extensive urban development in the coastal dune along the coast mainly for tourism use (Mayan Riviera).

Alvarado-Barrientos, Ma. Susana↗
DOE OSTI2026

AmeriFlux FLUXNET-1F MX-PMm Puerto Morelos mangrove

This is the AmeriFlux Management Project (AMP) created FLUXNET-1F version of the carbon flux data for the site MX-PMm Puerto Morelos mangrove. This is the FLUXNET version of the carbon flux data for the site MX-PMm Puerto Morelos mangrove produced by applying the standard ONEFlux (1F) software. Site Description - The tower was located at the “Dr. Alfredo Barrera Marín” Botanical Garden. The surface monitored is covered with basin mangrove (sporadically flooded wetland) that grows in a fringe parallel to the northeastern coast (ca. 1 km) of the Yucatan Peninsula. The dominant species are Rhizophora mangle and Conocarpus erectus, which grow intertwined and relatively stunted (max tree height is 5m). Under the influence of trade winds and frequent stroms. The vegetation is regenerating after complete defoliation due to hurricane Wilma (cat. 4) passing in October 2005. The site is sporadically flooded by rainfall soil saturation excess; there are no marine surface water inputs but ground water level fluctuations show tidal signals. The terrain of the monitored surface is flat, while the area downwind of the tower presents a slope which corresponds to an ancient coast line. There is extensive urban development in the coastal dune along the coast mainly for tourism use (Mayan Riviera).

Alvarado-Barrientos, Ma. Susana [Instituto de Ecol↗
DOE OSTI2014

Goals, Objectives, and Requirements (GOR) of the Ground-based Nuclear Detonation Detection (GNDD) Team for the Office of Defense Nuclear Nonproliferation Research and Development (DNN R&D)

The goal, objectives, and requirements (GOR) presented in this document define a framework for describing research directed specifically by the Ground-based Nuclear Detonation Detection (GNDD) Team of the National Nuclear Security Administration (NNSA). The intent of this document is to provide a communication tool for the GNDD Team with NNSA management and with its stakeholder community. It describes the GNDD expectation that much of the improvement in the proficiency of nuclear explosion monitoring will come from better understanding of the science behind the generation, propagation, recording, and interpretation of seismic, infrasound, hydroacoustic, and radionuclide signals and development of "game-changer" advances in science and technology.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
DOE OSTI2014

Ground-based Nuclear Detonation Detection (GNDD) Technology Roadmap

This GNDD Technology Roadmap is intended to provide guidance to potential researchers and help management define research priorities to achieve technology advancements for ground-based nuclear explosion monitoring science being pursued by the Ground-based Nuclear Detonation Detection (GNDD) Team within the Office of Nuclear Detonation Detection in the National Nuclear Security Administration (NNSA) of the U.S. Department of Energy (DOE). Four science-based elements were selected to encompass the entire scope of nuclear monitoring research and development (R&D) necessary to facilitate breakthrough scientific results, as well as deliver impactful products. Promising future R&D is delineated including dual use associated with the Comprehensive Nuclear-Test-Ban Treaty (CTBT). Important research themes as well as associated metrics are identified along with a progression of accomplishments, represented by a selected bibliography, that are precursors to major improvements to nuclear explosion monitoring.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
DOE OSTI2023

All-optical, Microwave-free NV-Diamond Magnetometer for High Magnetic Field Environment

Nitrogen vacancy (NV) magnetometry has commonly utilized microwave sources to manipulate the sensor's spin state. However, this technique becomes technically challenging under an environment with a Tesla-scale magnetic field or extreme conditions that prohibit the usage of microwave. By leveraging the effect that an off-axis magnetic field to the NV axis quenches its emitted photoluminescence, we present an all-optical, microwave-free broadband quantum diamond magnetometer. We demonstrate magnetic sensing over an extended bias magnetic field range — beyond the ground-state level anti-crossing (GSLAC) region — with a more integrated design.

Zheng, Xiechen↗
DOE OSTI2013

A 4-D Climatology (1979-2009) of the Monthly Tropospheric Aerosol Optical Depth Distribution over the Mediterranean Region from a Comparative Evaluation and Blending of Remote Sensing and Model Products

Since the 1980s several spaceborne sensors have been used to retrieve the aerosol optical depth (AOD) over the Mediterranean region. In parallel, AOD climatologies coming from different numerical model simulations are now also available, permitting to distinguish the contribution of several aerosol types to the total AOD. In this work, we perform a comparative analysis of this unique multiyear database in terms of total AOD and of its apportionment by the five main aerosol types (soil dust, seasalt, sulfate, black and organic carbon). We use 9 different satellite-derived monthly AOD products: NOAA/AVHRR, SeaWiFS (2 products), TERRA/MISR, TERRA/MODIS, AQUA/MODIS, ENVISAT/MERIS, PARASOL/POLDER and MSG/SEVIRI, as well as 3 more historical datasets: NIMBUS7/CZCS, TOMS (onboard NIMBUS7 and Earth- Probe) and METEOSAT/MVIRI. Monthly model datasets include the aerosol climatology from Tegen et al. (1997), the climate-chemistry models LMDz-OR-INCA and RegCM-4, the multi-model mean coming from the ACCMIP exercise, and the reanalyses GEMS and MACC. Ground-based Level- 2 AERONET AOD observations from 47 stations around the basin are used here to evaluate the model and satellite data. The sensor MODIS (on AQUA and TERRA) has the best average AOD scores over this region, showing a relevant spatiotemporal variability and highlighting high dust loads over Northern Africa and the sea (spring and summer), and sulfate aerosols over continental Europe (summer). The comparison also shows limitations of certain datasets (especially MERIS and SeaWiFS standard products). Models reproduce the main patterns of the AOD variability over the basin. The MACC reanalysis is the closest to AERONET data, but appears to underestimate dust over Northern Africa, where RegCM-4 is found closer to MODIS thanks to its interactive scheme for dust emissions. The vertical dimension is also investigated using the CALIOP instrument. This study confirms differences of vertical distribution between dust aerosols showing a large vertical spread, and other continental and marine aerosols which are confined in the boundary layer. From this compilation, we propose a 4-D blended product from model and satellite data, consisting in monthly time series of 3-D aerosol distribution at a 50 km horizontal resolution over the Euro-Mediterranean marine and continental region for the 2003–2009 period. The product is based on the total AOD from AQUA/MODIS, apportioned into sulfates, black and organic carbon from the MACC reanalysis, and into dust and sea-salt aerosols from RegCM-4 simulations, which are distributed vertically based on CALIOP climatology.We extend the 2003–2009 reconstruction to the past up to 1979 using the 2003–2009 average and applying the decreasing trend in sulfate aerosols from LMDz-OR-INCA, whose AOD trends over Europe and the Mediterranean are median among the ACCMIP models. Finally optical properties of the different aerosol types in this region are proposed from Mie calculations so that this reconstruction can be included in regional climate models for aerosol radiative forcing and aerosolclimate studies.

1979-2009↗
NASA NTRS1970

Image resolution: Its significance in a wildland area

The information content of simulated space photos as a function of various levels of image resolution was determined by identifying major vegetation-terrain types in a series of images purposely degraded optically to different levels of ground resolution resolvable distance. Comparison of cumulative interpretation results with actual ground truth data indicates that although there is definite decrease in interpretability as ground resolvable distance increases, some valuable information is gained by using even the poorest aerial photography. Developed is the importance of shape and texture for correct identification of broadleaf or coniferous vegetation types and the relative unimportance of shape and texture for the recognition of grassland, water bodies, and nonvegetated areas. Imagery must have a ground resolvable distance of at least 50 feet to correctly discriminate between primary types of woody vegetation.

Lauer, D. T.↗
NASA NTRS1972

Energy curves of CO2/-/.

Ab initio energy curves of the A super 2 sub 1 and B super 2 sub 1 states of CO2(-) have been obtained as a function of the bending angle. An analysis shows that gaseous CO2(-) in its ground vibrational level can have a relatively long life since the ion energy in the neighborhood of the ion equilibrium geometry is about 1 eV below the neutral molecule energy for that geometry.

Krauss, M.↗