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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 505 records · Page 28
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Ultrathin Visible-Light-Driven Mo Incorporating In 2 O 3 -ZnIn 2 Se 4 Z-Scheme Nanosheet Photocatalysts

Inspired by natural photosynthesis, the design of new Z-scheme photocatalytic systems is very promising for boosting the photocatalytic performance of H 2 production and CO 2 reduction, however, till now the direct synthesis of efficient Z-scheme photocatalysts remains a grand challenge. Herein, we demonstrate an interesting Z-scheme photocatalyst can be constructed by coupling In 2 O 3 and ZnIn 2 Se 4 semiconductors based on the theoretical calculations. Experimentally, we make a class of ultrathin In 2 O 3 -ZnIn 2 Se 4 (donated as In 2 O 3 -ZISe) spontaneous Z-scheme nanosheet photocatalysts for greatly enhancing the photocatalytic H 2 production. Furthermore, we incorporate Mo atoms to the Z-scheme In 2 O 3 -ZISe nanosheet photocatalyst by forming Mo-Se bond, confirmed by X-Ray photoelectron spectroscopy, in which the formed MoSe 2 works as co-catalyst of Z-scheme photocatalyst. As a consequence, such unique structure of In 2 O 3 -ZISe-Mo makes it exhibit 21.7 and 232.6 times higher photocatalytic H 2 evolution activity than those of In 2 O 3 -ZnIn 2 Se 4 nanosheet and In 2 O 3 nanosheets, respectively. And In 2 O 3 -ZISe-Mo is also very stable for photocatalytic H 2 production by showing almost no activity decay for 16 h test. Here, the ultraviolet-visible diffuse reflectance spectra, photoluminescence spectroscopy, transient photocurrent spectra and electrochemical impedance spectroscopy reveal that the enhanced photocatalytic performance of In 2 O 3 -ZISe-Mo is mainly attributed to its widened photoresponse range and effective carrier separation because of its special structure.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2018

Examination of lutetium(III)-DOTA and copper(II)-NOTA solution structures using EXAFS

Targeted radionuclide therapy generally relies on the chelation of select short-lived isotopes such as 177 Lu and 67 Cu. The majority of Lu(III) and Cu(II) chelate structural information is derived from solid state diffraction data. Herein, the complexes Lu(DOTA) - , Cu(NOTA) - were examined in solution using EXAFS for the first time. Both ligands were fully deprotonated and coordinated to the metal with four and three carboxylic sites for Lu(DOTA) - and Cu(NOTA) - , respectively. Near-neighbor correlations from nitrogen atoms on the macrocyclic cages were also visible in the spectra in addition to the adjacent carbon backbones. Coordination numbers, bond distances, and Debye-Waller factors are reported and discussed alongside differences with known crystal structures.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2015

Broadband sensitized white light emission of g-C{sub 3}N{sub 4}/Y{sub 2}MoO{sub 6}:Eu{sup 3+} composite phosphor under near ultraviolet excitation

The g-C{sub 3}N{sub 4}/Y{sub 2}MoO{sub 6}:Eu{sup 3+} composite phosphors were synthesized and characterized by X-ray diffraction, Fourier transform-infrared spectroscopy, ultraviolet visible diffuse reflection spectra, photoluminescence spectra and luminescence decay curves. Under the excitation of 360 nm near ultraviolet light, these composite phosphors show tunable emission from blue to red region, in which white light emission can be obtained in term of appropriate quality proportion of Y{sub 2}MoO{sub 6}:Eu{sup 3+} relative to g-C{sub 3}N{sub 4}/Y{sub 2}MoO{sub 6}:Eu{sup 3+}. In addition, the emission color can be also dependent on the excitation wavelength in g-C{sub 3}N{sub 4}/Y{sub 2}MoO{sub 6}:Eu{sup 3+} composite phosphor. - Graphical abstract: Under the excitation of 360 nm near ultraviolet light, the g-C{sub 3}N{sub 4}/Y{sub 2}MoO{sub 6}:Eu{sup 3+} composite phosphors show tunable emission from blue to red region, in which white light emission can be obtained. - Highlights: • The g-C3N4/Y2MoO6:Eu{sup 3+} composite phosphors were synthesized and characterized. • White light emission was realized in the g-C3N4/Y2MoO6:Eu{sup 3+} composites under UV excitation. • A novel idea to realize the broadband sensitized white light emission in phosphors was provided.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Design of a novel dual Z-scheme photocatalytic system composited of Ag{sub 2}O modified Ti{sup 3+} self doped TiO{sub 2} nanocrystals with individual exposed (001) and (101) facets

A novel dual Z-scheme photocatalytic system composited of Ag{sub 2}O nanocrystals modified Ti{sup 3+} self doped TiO{sub 2} nanocrystals with individual exposed (001) and (101) facets were successfully fabricated. In which, the Ti{sup 3+} self doped TiO{sub 2} nanocrystals with individual exposed (001) and (101) facets have been firstly prepared by a simple hydrothermal method, subsequently the as-prepared products were modified with Ag{sub 2}O nanocrystals through a sonochemical depositing process in order to build a novel dual Z-scheme photocatalytic system. The samples were carefully characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–visible diffuse reflectance spectra (UV–vis DRS), and Brunauer-Emmett-Teller (BET). The photocatalytic activity toward degradation of Rhodamine B (Rh B) aqueous solution under stimulated solar light was investigated. The experimental results showed this new dual Z-scheme photocatalytic system possess an enhanced photocatalytic degradation activity compared to that similar surface heterojunction photocatalysts composed of Ti{sup 3+} self doped TiO{sub 2} nanocrystals with individual exposed (001) and (101) facets. This novel photocatalytic system presents a high charge-separation efficiency and strong redox ability. This study will help us to better understand the photocatalytic mechanism of semiconductor photocatalysts with exposed different facets, and provide a new insight into the design and fabrication of advanced photocatalytic materials. - Highlights: •A novel dual Z-scheme system was built by Ag{sub 2}O and facet exposed TiO{sub 2} nanocrystals. •The individual TiO{sub 2} nanocrystals exposed (001) and (101) facets respectively. •Ag{sub 2}O coupled with Ti{sup 3+} self doped TiO{sub 2} nanocrystals through a sonochemical process. •The as-prepared sample possesses a super photocatalytic activity.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Growth and Characterization of Epitaxial FeWO 4 Thin Films with Controlled Oxygen Stoichiometry

Here, we report the growth of single-phase epitaxial FeWO 4 thin films, using plasma-assisted molecular beam epitaxy, and investigate structural, optical, and electronic properties. The FeWO 4 films grow in (100) orientation on c-plane sapphire (0001) substrates and exhibit 3 rotational twin variants where FeWO 4 [001] is aligned to sapphire [100] equivalent in-plane directions. X-ray diffraction measurements indicate that the epitaxial FeWO 4 (100) structure is optimized when 80-100 W of rf power is applied to an atomic oxygen source during growth, yielding films with minimal strain and impurity phases or other orientations. In films grown with 120 W of rf power, FeWO 4 crystallites develop inhomogeneous and homogeneous strains and are potentially contaminated with Fe 3+ oxide phase impurities. In films grown with 60 W of rf power, FeWO 4 crystallites do not form fully epitaxial layers. X-ray photoelectron spectroscopy indicates that the structural changes are correlated with the Fe 3+ /Fe 2+ oxidation state ratio increasing from 0.6-1.4 with rf power from 60-120 W. X-ray fluorescence spectroscopy indicates that the Fe/W composition ratio is also increasing from 1.1-1.8 with rf power from 60-120 W. Ultraviolet and visible optical absorption spectra indicate a 1.8 ± 0.1 eV band gap with an additional interband absorption feature at 3.1 ± 0.1 eV in the 80-100 W films, with similar onsets observed in the 60 W films. In the 120 W films, the higher lying transition is shifted to 2.7 ± 0.1 eV due to the Fe 3+ enrichment. Electrical resistivity decreases over 2 orders of magnitude with oxidation from 10 4 -10 5 Ω cm in 60 W films to 120 ± 10 Ω cm in 120 W films. Thermopower measurements show p-type to n-type conductivity conversion when oxidation states shift from Fe 2+ majority in the 100 W films to Fe 3+ majority in the 120 W films. We conclude that electron polaron hopping driven by Fe 3+ is a dominant transport mechanism and a source of n-type conductivity in overoxidized FeWO 4 films.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Metal-to-Ligand Charge-Transfer Spectrum of a Ru-Bipyridine-Sensitized TiO 2 Cluster from Embedded Multiconfigurational Excited-State Theory

Understanding optical properties of the dye molecule in dye-sensitized solar cells (DSSCs) from first-principles quantum mechanics can contribute to improving the efficiency of such devices. While density functional theory (DFT) and time-dependent DFT have been pivotal in simulating optoelectronic properties of photoanodes used in DSSCs at the atomic scale, questions remain regarding DFT’s adequacy and accuracy to furnish critical information needed to understand the various excited-state processes involved. In this work, we simulate the absorption spectra of a dye-sensitized solar cell analogue, comprised of a Ru-bipyridine (Ru-bpy) dye molecule and a small TiO2 cluster via DFT and via an accurate embedded correlated wavefunction (CW) theory. We generated CW spectra for the adsorbed Ru-bpy dye via a recently introduced capped density functional embedding theory or capped-DFET (to generate the embedding potential that accounts for the interaction of the molecule and the TiO 2 cluster). We then combined capped-DFET with the accurate but expensive multiconfigurational complete active space second-order perturbation theory (CASPT2)—embedded CASPT2. Because the CW theory is conducted on only a portion of the total system in the presence of an embedding potential that describes that portion’s interaction with its environment, we efficiently obtain CW-quality predictions that reflect local properties of the entire system. Specifically, for example, with capped-DFET and embedded CW theory, we can simulate accurately a plethora of metal-to-ligand charge-transfer excited properties at a manageable computational cost. Here, we predict detailed electronic spectra within the visible region, featuring the lowest three singlet and triplet excited states, along with predictions of the singlets’ lifetimes. We illustrated these results using a Jablonski diagram that show the relative energy position of the singlet and longer-lived triplet excited states and analyzed and proposed relaxation paths for the excited state corresponding to the most intense but short-lived absorption (interconversion, intersystem crossing, fluorescence, and phosphorescence) that may lead to longer-lived excited states necessary for efficient charge separation required to generate current in solar cells.

14 SOLAR ENERGY↗
DOE OSTI2017

Tunable UV-Emitters through Graphene Plasmonics

Control over the spontaneous emission of light through tailored optical environments remains a fundamental paradigm in nanophotonics. The use of highly confined plasmons in materials such as graphene provides a promising platform to enhance transition rates in the IR-THz by many orders of magnitude. However, such enhancements involve near-field plasmon modes or other kinds of near-field coupling like quenching, and it is challenging to use these highly confined modes to harness light in the far-field due to the difficulty of plasmonic outcoupling. Here in this paper, we propose that through the use of radiative cascade chains in multilevel emitters, IR plasmons can be used to enhance far field spectra in the visible and UV range, even at energies greater than 10 eV. Combining Purcell-enhancement engineering, graphene plasmonics, and radiative cascade can result in a new type of UV emitter whose properties can be tuned by electrically doping graphene. Varying the distance between the emitter and the graphene surface can change the strength of the far-field emission lines by 2 orders of magnitude. We also find that the dependence of the far-field emission on the Fermi energy is potentially extremely sharp at the onset of interband transitions, allowing the Fermi energy to effectively serve as a “switch” for turning on and off certain plasmonic and far-field emissions.

42 ENGINEERING↗
DOE OSTI2026

Photovoltage behaviour of p-Sb 2 S 3 photocathodes for hydrogen evolution: effect of n-In 2 S 3 passivation layers

The 1.76 eV band gap of antimony(iii) sulphide (Sb 2 S 3 ) makes this semiconductor material a promising light absorber for photoelectrochemical water splitting, but scalable fabrication approaches to efficient devices are still lacking. Here we show that compact Sb 2 S 3 films on FTO can be obtained by electrochemical growth from aqueous colloidal sulphur and antimony trichloride solutions, followed by mild annealing. These films can be converted into hydrogen evolution photocathodes after coating with In 2 S 3 passivation layers and the addition of Pt proton reduction co-catalysts. For the first time, vibrating Kelvin probe surface photovoltage (VKP-SPV) spectroscopy is used to observe the carrier dynamics in such photoelectrodes. While the bare Sb 2 S 3 films suffer from high surface recombination rates and poor electron extraction, the In 2 S 3 overlayer is found to raise the photovoltage and cathodic photocurrent density, due to passivation of surface defects and formation of a p–n heterojunction. In thick In 2 S 3 films, these benefits are offset by shading and slow electron transfer. Also, we find that O 2 strongly affects the band bending in the Sb 2 S 3 –air and In 2 S 3 –air junctions and their photovoltage. The optimised devices evolve H 2 at 77.5% Faradaic efficiency and with 0.084% applied bias photon-to-current efficiency (ABPE) at 0.12 V vs. RHE. The low ABPE value is attributed to Sb 2 S 3 sub-bandgap defects visible in SPV spectra, the random orientation of Sb 2 S 3 crystallites in the films, which inhibits charge transport, the absence of crystal facets of Sb 2 S 3 , and a detrimental Schottky junction at the FTO|Sb 2 S 3 interface.

de Araújo, Moisés A. [University of California, Da↗
DOE OSTI2014

Synthesis of few layer graphene by direct exfoliation of graphite and a Raman spectroscopic study

The exfoliation of graphene from pristine graphite in a liquid phase was achieved successfully via sonication followed by centrifugation method. Ultraviolet–visible (UV–vis) spectra of the obtained graphene dispersions at different exfoliation time indicated that the concentration of graphene dispersion increased markedly with increasing exfoliation time. The sheet-like morphology of the exfoliated graphene was revealed by Scanning Electron Microscopy (SEM) image. Further, the morphological change in different exfoliation time was investigated by Atomic Force Microscopy (AFM). A complete structural and defect characterization was probed using micro-Raman spectroscopic technique. The shape and position of the 2D band of Raman spectra revealed the formation of bilayer to few layer graphene. Also, Raman mapping confirmed the presence of uniformly distributed bilayer graphene sheets on the substrate.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Energy band gap and spectroscopic studies in Mn{sub 1-x}Cu{sub x}WO{sub 4} (0 ≤ x ≤ 0.125)

A study on the effect of nonmagnetic Cu{sup 2+} substitution at Mn{sup 2+} site on the structural and energy band gap of the MnWO{sub 4} is reported. Convenient solid state reaction route has been adopted for the synthesis of Mn{sub 1-x}Cu{sub x}WO{sub 4}. X-ray diffraction (XRD) pattern showed high crystalline quality of the prepared samples. Raman spectroscopic studies were carried out to understand the structural aspects of the doping. 15 Raman active modes were identified out of 18, predicted for wolframite type monoclinic structure of MnWO{sub 4}. UV-visible diffuse reflectance spectra were recorded and analyzed to get energy band gap of the studied system and are found in the range of 2.5 eV to 2.04 eV with a systematic decrease with the increase in Cu{sup 2+} concentration. Energy band gap values are verified by Density Functional Theory calculations based on projector augmented wave (PAW) method. The calculated values are in good agreement with the experimental data.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Effect of Gd substitution on the structural, magnetic, and magnetocaloric properties of HoCrO 3

Rare-earth chromites are a novel type of magnetoelectric multiferroics. Here, a Ho 0.33 Gd 0.67 CrO 3 powder sample was synthesized via a citrate route, and the structural properties were characterized by X-ray diffraction, scanning electron microscopy, and the Raman technique. The UV-Visible optical absorbance spectra were also measured in the wavelength range of 200–800 nm. The valence state of Cr was found to be purely 3+ according to the X-ray photoelectron spectroscopy. The temperature-dependent dielectric constant and loss tangent data measured between the frequencies of 1 kHz and 1 MHz show no anomalies around the magnetic transition temperature of the material. The dc magnetization measurements show that the ordering temperature of Cr 3+ ( T N C r ) is 155 K for Ho 0.33 Gd 0.67 CrO 3 , which is larger than 140 K for HoCrO 3 . The positive slope of the Arrott plots from 0 T to 7 T reveals that the antiferromagnetic-paramagnetic phase transition is second-order in nature. At a field of 7 T, the Ho 0.33 Gd 0.67 CrO 3 sample showed a giant magnetocaloric entropy change, -ΔS, of ~23.3 J/kg K at 5 K, and a refrigeration capacity of ~481.2 J/kg, which are much higher than those of pure bulk HoCrO 3 . This renders this material prospective for magnetic refrigeration in the low temperature (<30 K) range.

36 MATERIALS SCIENCE↗
DOE OSTI2015

EFFECT OF UV RADIATION ON THE SPECTRAL FINGERPRINTS OF EARTH-LIKE PLANETS ORBITING M STARS

We model the atmospheres and spectra of Earth-like planets orbiting the entire grid of M dwarfs for active and inactive stellar models with T{sub eff} = 2300 K to T{sub eff} = 3800 K and for six observed MUSCLES M dwarfs with UV radiation data. We set the Earth-like planets at the 1 AU equivalent distance and show spectra from the visible to IR (0.4–20 μm) to compare detectability of features in different wavelength ranges with the James Webb Space Telescope and other future ground- and spaced-based missions to characterize exo-Earths. We focus on the effect of UV activity levels on detectable atmospheric features that indicate habitability on Earth, namely, H{sub 2}O, O{sub 3}, CH{sub 4}, N{sub 2}O, and CH{sub 3}Cl. To observe signatures of life—O{sub 2}/O{sub 3} in combination with reducing species like CH{sub 4}—we find that early and active M dwarfs are the best targets of the M star grid for future telescopes. The O{sub 2} spectral feature at 0.76 μm is increasingly difficult to detect in reflected light of later M dwarfs owing to low stellar flux in that wavelength region. N{sub 2}O, another biosignature detectable in the IR, builds up to observable concentrations in our planetary models around M dwarfs with low UV flux. CH{sub 3}Cl could become detectable, depending on the depth of the overlapping N{sub 2}O feature. We present a spectral database of Earth-like planets around cool stars for directly imaged planets as a framework for interpreting future light curves, direct imaging, and secondary eclipse measurements of the atmospheres of terrestrial planets in the habitable zone to design and assess future telescope capabilities.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

Successive neutron alignments in the yrast, negative-parity band of oblate-deformed Tl 199

The negative-parity band structure built on the proton h 9/2 state in 199 Tl has been established up to an excitation energy of 7 MeV and spin of (51/2) ℏ. The level scheme has been extended with the inclusion of fourteen new transitions de-exciting levels at high spin. The ΔI = 1 γ rays are found to be more prominently visible in the spectra when comparing to Δ I = 2 transitions. Rotation alignments are evident at frequencies of 0.22 and 0.30 MeV with both being attributed to the breaking of pairs of neutrons in the i 13/2 subshell. Since 199 Tl is expected to have weak oblate deformation, and lies in a transitional region where competing contributions to the spin are expected from collective rotation and the angular momentum of high-j nucleons, calculations using both the principal axis cranking (PAC) and tilted axis cranking (TAC) formalisms have been performed to understand its structure. Both the PAC and TAC calculations are found to provide a satisfactory description of the evolution of excitation energies with spin. The PAC calculations give a good account of the experimental crossing frequencies and associated spins. Furthermore, the structure of the yrast, negative-parity band in 199 Tl may be primarily understood in terms of the collective rotation of a moderately deformed oblate nucleus, along with contributions to the angular momentum from two pairs of rotation-aligned i 13/2 neutrons.

190 ≤ A ≤ 219↗
DOE OSTI2019

Measuring Magnetic Fields in Collisionless Experiments

Magnetic field and electron density diagnostics are critical tools in the characterization of high energy density laboratory plasmas. These plasma environments are complex and the magnetic fields and electron densities often exhibit significant spatial and temporal variation leading to significant challenges in these measurements. Even the most promising technique, Zeeman splitting, faces challenges under plasma conditions where broadening due to high density and temperature is greater than the Zeeman splitting. Here we propose and describe a diagnostic based on Zeeman broadening. The Zeeman broadening diagnostic relies on measuring the widths of multiplet components simultaneously. The method does not depend on resolved lines, but rather on measuring the difference in the widths of multiplet lines. Experiments were performed at the University of Nevada, Reno, Nevada Terawatt Facility (NTF). The Zeeman broadening diagnostic gathered visible broadened multiplet spectra from laser produced plasmas, and plasmas generated from wire-arrays driven by the Zebra z-pinch pulsed power apparatus. The laser produced plasma, created by the Leopard pulsed laser (I>1014 W/cm 2 ), evolved in an external magnetic field (B<40T) generated by current driven through a solid electrode by the Zebra current pulse. For laser produced plasmas, observation of the magnetic field radial profile showed that the external field completely diffuses into the plasma after approximately 100 ns. Further, as the plasma continues to evolve, the field profiles within the plasma develop modulations that do not map the external field profile. For the wire array experiments, radial electron density, and magnetic field, profiles were measured. Here the Zeeman splitting was not resolved and the magnetic fields were determined from the difference between the widths of the multiplet line profiles. Thus, it has been demonstrated that Zeeman broadening may be used as a magnetic field diagnostic.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1975

Combustion of bulk titanium in oxygen

The combustion of bulk titanium in one atmosphere oxygen is studied using laser ignition and several analytical techniques. These were high-speed color cinematography, time and space resolved spectra in the visible region, metallography (including SEM) of specimens quenched in argon gas, X-ray and chemical product analyses, and a new optical technique, the Hilbert transform method. The cinematographic application of this technique for visualizing phase objects in the combustion zone is described. The results indicate an initial vapor phase reaction immediately adjacent to the molten surface but as the oxygen uptake progresses the evaporation approaches the point of congruency and a much reduced evaporation rate. This and the accumulation of the various soluble oxides soon drive the reaction zone below the surface where gas formation causes boiling and ejection of particles. The buildup of rutile cuts off the oxygen supply and the reaction ceases.

Clark, A. F.↗
NASA NTRS1980

A laboratory study of magnesium-tetrabenz-porphyrin - Lack of agreement with diffuse interstellar bands

The visible and infrared spectra and thermal behavior of the bis-pyridal-magnesium-tetrabenz-porphyrin molecule proposed as the carrier of the diffuse interstellar bands were measured. Of the six band coincidences reported by Johnson (1977), only one, 4430 A, occurs in these experiments. This coincidence requires a special environment, not likely to occur in interstellar space but the infrared spectrum does not support Johnson's vibrational scheme. These spectroscopic and thermal measurements contradict the hypothesis that this molecule causes the diffuse bands.

Donn, B.↗
NASA NTRS1981

Are we beginning to understand T Tauri stars

An international meeting of astronomers in April 1981 in Portugal to discuss recent data on T Tauri stars is described. It is pointed out that T Tauri stars all vary irregularly in brightness, occur in intimate association with dusty molecular clouds, and exhibit bright optical emission lines, principally of hydrogen, helium, and iron. Stars with masses roughly 0.2 to three times the sun's and with ages from 100,000 to 1,000,000 years are typical of the T Tauri regime. It is thought that the often rich emission-line spectra seen at visible wavelengths indicate the presence of a stellar chromosphere, where the temperature rises steeply from the usual cool photospheric values around 4,000 to 5,000 K. Even though a recent extensive survey of T Tauri stars has been completed, no clear role for rotation in producing radio emission or stellar winds has yet emerged.

Cohen, M.↗
NASA NTRS1981

Spectral reflectance of hydrophytes

Identification of hydrophytes will improve the delineation and classification of wetlands on remotely sensed imagery. Spectral reflectance measurements of 10 species of hydrophytes were made with an Exotech radiometer during three phenological stages, flowering and early seed, senescent, and early emergent. Reflectance data were analyzed to determine significant (P not greater than 0.5) differences between species in each of four spectral regions during each phenological stage. Eight species had significantly (P not greater than 0.05) different reflectances during the flower and early seed stage. Among the ten species only one could not be spectrally isolated during at least 1 phenological stage. The results indicate that films sensitive to both visible and infrared spectra (e.g., Ektachrome infrared) should enable recognition of different species of hydrophytes.

Best, R. G.↗