Radar backscatter and rocket probe measurements of electron temperature above Arecibo
Comparison of radar backscatter and rocket probe measurements of ionospheric electron temperature
Brace, L. H.↗
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Numerical simulation of a disk-shaped electron accelerating electrostatic probe
This paper presents a method utilizing the numerical plasma simulation particle-in-cell technique for studying electron accelerating probe characteristics. A probe configuration other than the commonly used plane, cylindrical, or spherical case will be studied; the probe configuration used is that of a disk. Cylindrical geometry is used in the simulation model. One of the advantages of a numerical simulation is the ease with which the details of the system can be examined. Therefore, in addition to the current-voltage characteristics of the static probe, other results are presented such as the time evolution of the plasma properties and studies of the sheath region surrounding the probe.
Nonnast, J. H.↗
X-Ray Diffraction and Reflectance Spectroscopy of Murchison Powders (CM2) After Thermal Analysis Under Reducing Conditions to Final Temperatures Between 300 and 1300°c
The asteroids Ryugu and Bennu have spectral characteristics in common with CI/CM type carbonaceous chondrites and are target bodies for JAXA’s Hayabusa2 and NASA’s OSIRIS-Rex missions, respectively. Analog studies, based primarily on the Murchison CM2 chondrite, provide a pathway to separate spectral properties resulting space weathering from those inherent to parent-body, mineralogy, chemistry, and processes. Ryugu shares spectral properties with thermally metamorphosed and partly dehydrated CI/CM chondrites. We have undertaken a multidisciplinary study of the thermal decomposition of Murchison powder samples as an analog to metamorphic process that may have occurred on Ryugu. Bulk analyses include thermal And evolved gas analysis, X-ray diffraction (XRD), and VIS-NIR and Mössbauer spectroscopy; micro- to nanoscale analyses included scanning and transmission electron microscopy and electron probe micro analysisWe report here XRD and VIS-NIR analyses of pre- and post-heated Murchison powders, and in a companion paper report results from multiple electron beam techniques.
Morris, R. V.↗
Probe and radar electron temperatures in an isotropic, nonequilibrium plasma
Electron temperatures measured by electrostatic probes and radar backscatter in isotropic, nonequilibrium plasma for studying planetary atmospheres
Hoegy, W. R.↗
Electronics and Sensor Cooling with a Stirling Cycle for Venus Surface Mission
The inhospitable ambient surface conditions of Venus, with a 450 C temperature and 92 bar pressure, may likely require any extended-duration surface exploratory mission to incorporate some type of cooling for probe electronics and sensor devices. A multiple-region Venus mission study was completed at NASA GRC in December of 2003 that resulted in the preliminary design of a kinematically-driven, helium charged, Stirling cooling cycle with an estimated over-all COP of 0.376 to lift 100 watts of heat from a 200 C cold sink temperature and reject it at a hot sink temperature of 500 C. This paper briefly describes the design process and also describes and summarizes key features of the kinematic, Stirling cooler preliminary design concept.
Mellott, Ken↗
Cure Monitoring
Micromet Instruments Inc. manufactures the Eumetric System II Microdielectrometer, key to which is a miniature electronic probe - a silicon microchip that contains electrodes and circuitry for measuring the electrical properties of whatever material is placed in contact with the electrodes. The rest of the system consists of additional sensors, electronic components, microcomputers, modules, and software.
Source record↗
Relation between integral electron flux and current in retarding-potential plasma probes
Integral electron flux and current in retarding- potential plasma probes, considering application to nonconcave geometry and spacecraft probes
Matthews, D. L.↗
Digital multichannel photometry with digicons
The digital system is described and compared to other sensor systems. The digicon system starts with a photocathode, has magnetic focusing of the accelerated photoelectrons, and the electrons hit an array of solid-state diodes. These characteristics, however, are the only ones which are applicable to both the digicon and the other systems. With the digicon system, instead of attempting to read the resulting charges on the diodes by probing electrons, or by a charge transfer out, an actual physical wire is connected to each separate diode. This provides a huge advantage in improved signal-to-noise ratio.
Mcilwain, C. E.↗
Diffusion of chromium and aluminum in Ni-20Cr and TDNiCr /Ni-20Cr-2ThO2/.
Diffusion coefficients have been measured for Cr51 in fine- and coarse-grained TDNiCr (Ni-20Cr-2ThO2) and in fine-grained Ni-20Cr in the temperature range from 1038 to 1200 C. Selective diffusivities have also been determined for specimens of these alloys which were aluminized to give an initial surface concentration of 5.8 wt % Al. Finally, diffusion coefficients for interdiffusion of aluminum in TDNiCr and Ni-20Cr have been obtained from electron probe microanalysis of the aluminized specimens. For a given grain size and temperature there is no difference in diffusivities for chromium diffusion in TDNiCr or Ni-20Cr. Diffusion coefficients increase with decreasing grain size for both alloys. Comparison of aluminum diffusion data obtained from electron microprobe profiles with radiotracer chromium diffusivities suggests that aluminum diffuses approximately three times faster than chromium in TDNiCr and Ni-20Cr.
Seltzer, M. S.↗
Measuring Changes In Dimensions Of Turbine Blades
Mechanical fixture and electronic gauge probe surface before and after fabrication processes. Assembly of commercially available devices measures changes in dimensions of irregularly shaped part. Turbine blade clamped on rotary table touched by probe of electronic depth gauge. Positioned by micrometers of three-axis translation stage, probe just touches blade. Assembly developed specifically to measure thickness of material added to or removed from surface of turbine blade during fabrication processes.
Woodford, William H.↗
Microstructural stability of wrought, laser and electron beam glazed NARloy-Z alloy at elevated temperatures
Microstructure of wrought, laser, and electron-beam glazed NARloy-Z(Cu-3 wt.% Ag-0.5 wt.% Zr) was investigated for thermal stability at elevated temperatures (539 to 760 C (1,100 to 1,400 F)) up to 94 h. Optical and scanning electron microscopy and electron probe microanalysis were employed for studying microstructural evolution and kinetics of precipitation. Grain boundary precipitation and precipitate free zones (PFZ's) were observed in the wrought alloy after exposing to temperatures above 605 C (1,120 F). The fine-grained microstructure observed in the laser and electron-beam glazed NARloy-Z was much more stable at elevated temperatures. Microstructural changes correlated well with hardness measurements.
Singh, J.↗
Zircon, Baddeleyite, and Reidite Found in Ries Crater Suevite
Introduction: Impact events can generate superheated impact melts and even vapor [1]. In the past decade, evidence of the high temperatures and high pressures of the impact process has been found in the impact melt from terrestrial craters (e.g., Mistastin Lake [2], Meteor Crater [3]) and even on the Moon [4–5]. Often, these studies involve zircon or zirconium-bearing phases. Zircon is a particularly useful mineral, due to its robustness and durability against weathering. It is used principally for chronology, but it has a multitude of geologic applications, including geothermometry and fingerprinting magma sources. Here we focus on its capability of recording impact conditions. Grains of zircon (ZrSiO4) are converted at high temperature and/or pressure during an impact event to reidite (a high-pressure polymorph of ZrSiO4) or to tetragonal-ZrO2 + SiO2 [6]. Reidite and tertragonal-ZrO2 leave identifying relicts in the rocks, markers of the high pressures and/or temperatures these rocks underwent. Ries Crater is a 26-km-diameter peak ring crater in southern Germany that formed approximately 15 Ma [7–9]. Ries is the type locality of the polymict impact breccia known as suevite. Here, we report a microanalytical study of suevite from the Ries impact structure. These analyses are used to inform our understanding of the pressure and temperature conditions involved in creating a polymict impact breccia such as suevite in a peak ring crater. Sample Description: The sample, denoted 16RS08, originates from Otting Quarry, at 48.8777° N, 10.7921° E, approximately 17 km from the center of the Ries Crater in Germany (approximately 4 km outside the crater rim). The material recorded in sample 16RS08 is therefore considered an outer suevite. The outer suevite is a discontinuous layer of polymict impact breccia that occurs outside the central ring of Ries, up to 22 km from the center of the crater [9]. Lithic clasts in the outer suevite consist primarily of crystalline basement rocks (gneiss, granite, amphibolite), with less than 5% of lithic clasts being overlying sedimentary rocks (limestone, sandstone, shale) [9]. The thin section studied contains variably shocked lithic and mineral clasts, impact glass, and interstitial minerals that make up the matrix of the breccia (Fig. 1) [9]. Methods: We used a Cameca SX100 electron probe microanalyzer (EPMA) located in the Kuiper Materials Imaging and Characterization Facility (KMICF) at the University of Arizona to obtain 15 elemental X-ray maps of 16RS08. We next used the JEOL 7900F SEM at the Astromaterials Research & Exploration Science (ARES) at NASA Johnson Space Center (JSC) to obtain electron backscatter diffraction (EBSD) maps and energy dispersive X-ray spectroscopy (EDS) maps of select portions of the section. The EBSD data were collected under beam conditions of 20 kV, and ~9 μA, with step sizes varying from 0.05 to 2 μm. Following EBSD data collection, we processed the data using AZtecCrystal and MTEX, a free MATLAB toolbox. Results: We used the elemental X-ray maps to identify the areas of interest in the section, particularly phosphates and Zr-bearing grains. These areas of interest were then targeted for follow up EBSD and EDS analyses. We have identified, through combined EBSD and EDS analysis, the presence of zircon, reidite, and monoclinic-ZrO2 (baddeleyite) in 16RS08. In 16RS08, we have found singular grains of zircon, zircon with a vermicular baddeleyite halo (Fig. 2a), and granular zircon with reidite (Fig. 2b). The different Zr-rich phases and their corresponding textures signifies that this sample underwent a broad spectrum of pressure and temperature conditions during the impact event. For example, zircons surrounded by a vermicular baddeleyite and SiO2 intergrowth (i.e., Fig. 2a) have been shown to preserve evidence of the extremely high temperatures of impact melt, upwards of 2370 °C [2, 6]. Similarly, reidite and granular zircon (i.e., Fig. 2b) have been shown to preserve evidence of high pressure, as the transition to reidite occurs >30 GPa [3, 6]. Future Work: Next, we will process the EBSD and EDS data for these Zr-rich grains, specifically looking for indicators of cubic- or tetragonal-ZrO2 in the baddeleyite remnants and of shock-precursors to the reidite. To further inform our work, we will also obtain BSE images of these grains using a Hitachi S-4800 SEM in KMICF at the University of Arizona, as well as geochemical spot analyses via EPMA. The data collected will be used to constrain the formation conditions of the Ries Crater outer suevite. Acknowledgments: We thank Ken Domanik and Jerry Chang for their support with data collection. This work was supported by a University of Arizona RII Core Facilities Pilot Program grant and start-up funds to JJB. TME thanks A. Cavosie and N. Timms for assistance during field sampling. We acknowledge support from NASA’s Planetary Science Research program for analysis performed at JSC. References: [1] Melosh H. J. (1989) Oxf. U. Press. [2] Timms et al. (2017) EPSL 477, 52–58. [3] Cavosie et al. (2016) Geology 44:9, 703–706. [4] White et al. (2020) Nature Astr. 4, 974–978. [5] Crow C. A. et al. (2017) GCA 202, 264–284. [6] Timms et al. (2017) Earth-Sci. Rev. 165, 185–202. [7] Schmieder M. et al. (2018) GCA 220, 146–157. [8] Schwarz W. H. et al. (2020) M&PS 55:2, 312–325. [9] Stöffler et al. (2013) M&PS 43:4, 515–589.
Zircon↗
Pink Spinel in Apollo Impact Melt Rock 68815: Implications for Mg-Suite Magmatism
Introduction: Magnesian rocks from the lunar highlands are collectively termed the Mg-suite. Characterized by high (>60) Mg# (molar 100×Mg/[Mg+Fe]) in mafic phases and calcic plagioclase, these rocks are plutonic to hypabyssal in origin, and include a range of bulk mineralogies such as troctolites, dunites, norites, gabbronorites, and spinel troctolites [1]. These Mg-suite lithologies have distinct trace element concentrations and ratios that differentiate them from other lunar rock types. These rocks are ancient, generally dated to between 4.5 and 4.1 Ga, although it is unknown if this represents the full range of Mg-suite ages [1–2]. Among the Mg-suite lithologies, the spinel troctolites are relatively rare, to date only found in polymict breccias [3]. Spinel troctolites, as their name suggests, consist of calcic plagioclase and forsteritic olivine, with minor amounts of spinel (MgAl2O4), ± pyroxene and cordierite [1,4]. This form of spinel is often called ‘pink’ spinel because of its appearance in thin section under plane polarized light (PPL; Fig. 1), due to minor amounts of Cr. Spinel troctolites are generally plutonic or hypabyssal in origin (subsequently exhumed and incorporated into polymict breccias), or formed through impact processes (e.g., crystalline impact melt) [5]. A spinel-rich lithology has also been found in the Moscoviense region of the Moon via the Moon Mineralogy Mapper (M3) and lacks other mafic phases [6]. Finally, while the Mg-suite sampled thus far consists of plutonic (or hypabyssal) rocks, the question remains if such magmas could have erupted on the surface of the Moon [7]. These magmas have much lower density than mare basalts, but little sample or remote sensing evidence has been found to support the idea that extrusive Mg-suite volcanism occurred [7]. Here, we present a coordinated microanalytical study of spinel-bearing lithic and mineral clasts found in Apollo sample 68815. These data will be used to understand their petrogenesis (magmatic or impact) and modification histories, and to shed light on the existence of volcanic Mg-suite rocks. Sample Description: Apollo sample 68815 is a polymict impact melt breccia containing a variety of lithic and mineral fragments embedded in devitrified impact melt. This sample was chipped off the top of a boulder at Station 8 during the Apollo 16 mission and had an original weight of nearly 1.8 kg. In this study, we investigated two polished thin sections of 68815: 68815,17 and 68815,148, both containing spinel. Methods: The thin sections of 68815 were studied using optical light microscopy (PPL, cross-polarized light, and reflected light) with a Keyence VHX-7100 Digital Microscope. Each section was then X-ray mapped for 13–14 elements using a Cameca SX100 electron probe microanalyzer (EPMA) located in the Kuiper Materials Imaging and Characterization Facility (KMICF) at the University of Arizona. We have obtained geochemical information about the phases (olivine, plagioclase, spinel, pyroxene) in the thin sections also using the EPMA. In addition, we have used ThermoScientific Helios NanoLab 660 Focused-Ion-Beam Scanning-Electron Microscope (FIB-SEM) and a Hitachi S-4800 SEM (both in KMICF) to obtain backscattered electron (BSE) images and energy dispersive Xray spectrometry (EDS) maps of areas of interest. Using a JEOL 7900F SEM at the Astromaterials Research & Exploration Science (ARES) at NASA Johnson Space Center (JSC), we have obtained electron backscatter diffraction (EBSD) maps of the spinel-bearing portions of the thin sections. The EBSD data were collected under beam conditions of 20 kV, and ~90 μA, with step sizes varying from 0.05 to 2 μm. Following EBSD data collection, we processed the data using AZtecCrystal and MTEX, a free MATLAB toolbox. Results: We have found clasts with subophitic textures, that consist of primarily olivine and plagioclase, with minor amounts of pink Mg-Al spinel and pyroxene (Fig. 1). These clasts are up to ~1 mm in length and contain spinels up to 50 μm across. We have additionally identified pink Mg-Al spinels within the impact melt (i.e., not contained in lithic clasts) in both thin sections. In one instance, a single spinel grain is approximately 300 μm across (Fig. 1b, 2). The spinel fragments embedded in impact melt have varying compositions, typically distinct from the compositions of spinels in the lithic clasts. Spinel-Bearing Clasts: Ten lithic clasts with similar textures and mineral compositions were identified between 68815,17 (two clasts) and ,148 (eight clasts). These clasts fall into two groups. The first has skeletal olivine with intergranular plagioclase, with minor amounts of pyroxene and spinel (Fig. 1a, 2c, 2d). The spinel in these clasts are found amid the plagioclase. The second group have an intergranular texture of olivine and plagioclase, again with minor spinel and pyroxene. The second group may contain spinels surrounded by plagioclase, and spinels enclosed in olivine. Spinels located within both clast types range from no apparent Cr zoning, to reverse zoning (Cr-enrichment inward; Fig. 2d), to normal zoning (Cr-enrichment outward). In the clasts thus far investigated with EPMA, plagioclase compositions range from An# (molar 100×Ca/[Ca+Na+K]) 92–96. Olivine Mg# ranged from 77 to 94, while pyroxene had Mg# from 54–84. Spinel in the clasts have Cr# (molar 100×Cr/[Cr+Al]) 2–4 and Mg# 88–91, which is within the range of pristine and plutonic spinel troctolites [8]. Isolated Spinels: These crystals are generally euhedral to subhedral, and can exhibit reverse Cr zoning (Cr enrichment inward) or no apparent Cr zoning. The spinels thus far investigated via EPMA have Cr# 9–14 and Mg# 65–82. The Cr# for these spinels is within the range reported by [8], but have lower Mg#. Future Work: We will continue to process the EBSD data for these lithic and mineral clasts. We will also continue to characterize these clasts using EPMA and SEM. By thoroughly characterizing the various spinels and spinel-bearing clasts, we aim to constrain the petrogenesis of these minerals and rock fragments. Acknowledgments: We thank NASA for the loan of these thin sections. We thank Ken Domanik and Jerry Chang for their support with data collection. Work was supported by a University of Arizona RII Core Facilities Pilot Program grant and start-up funds to JJB. We acknowledge support from NASA’s Planetary Science Research program for analysis performed at JSC. References: [1] Shearer C. K. et al. (2015) Am. Min. 100, 294–325. [2] Borg L. E. et al. (2020) GCA 290, 312–332. [3] Warren P. H. (1993) Am. Min. 78, 360–376. [4] Dymek R. F. et al. (1976) LPS VII, 2335–2378. [5] Treiman et al. (2019) Am. Min. 104, 370–384. [6] Pieters et al. (2011) JGR: Plan. 116:E00G08. [7] Prissel et al. (2016) Icarus 277, 319–329. [8] Prissel et al. (2016) Am. Min. 101, 1624–1635.
spinel↗
Silicon Carbide Solar Cells Investigated
The semiconductor silicon carbide (SiC) has long been known for its outstanding resistance to harsh environments (e.g., thermal stability, radiation resistance, and dielectric strength). However, the ability to produce device-quality material is severely limited by the inherent crystalline defects associated with this material and their associated electronic effects. Much progress has been made recently in the understanding and control of these defects and in the improved processing of this material. Because of this work, it may be possible to produce SiC-based solar cells for environments with high temperatures, light intensities, and radiation, such as those experienced by solar probes. Electronics and sensors based on SiC can operate in hostile environments where conventional silicon-based electronics (limited to 350 C) cannot function. Development of this material will enable large performance enhancements and size reductions for a wide variety of systems--such as high-frequency devices, high-power devices, microwave switching devices, and high-temperature electronics. These applications would supply more energy-efficient public electric power distribution and electric vehicles, more powerful microwave electronics for radar and communications, and better sensors and controls for cleaner-burning, more fuel-efficient jet aircraft and automobile engines. The 6H-SiC polytype is a promising wide-bandgap (Eg = 3.0 eV) semiconductor for photovoltaic applications in harsh solar environments that involve high-temperature and high-radiation conditions. The advantages of this material for this application lie in its extremely large breakdown field strength, high thermal conductivity, good electron saturation drift velocity, and stable electrical performance at temperatures as high as 600 C. This behavior makes it an attractive photovoltaic solar cell material for devices that can operate within three solar radii of the Sun.
Bailey, Sheila G.↗
Adrianite, Ca12(Al4Mg3Si7)O32Cl6, a New Cl-rich Silicate Mineral From the Allende Meteorite: An Alteration Phase in a Ca-Al-rich Inclusion
Adrianite (IMA 2014-028), Ca12(Al4Mg3Si7)O32Cl6, is a new Cl-rich silicate mineral and the Si,Mg analog of wadalite. It occurs with monticellite, grossular, wadalite, and hutcheonite in altered areas along some veins between primary melilite, spinel, and Ti,Al-diopside in a Type B1 FUN (Fractionation and Unidentified Nuclear effects) Ca-Al-rich inclusion (CAI), Egg-3, from the Allende CV3 carbona-ceous chondrite. The mean chemical composition of type adrianite by electron probe microanalysis is (wt%) CaO 41.5, SiO2 27.5, Al2O3 12.4, MgO 7.3, Na2O 0.41, Cl 13.0, O=Cl –2.94, total 99.2, giving rise to an empirical formula of (Ca11.69Na0.21)(Al3.85Mg2.88Si7.23)O32Cl5.80. The end-member formula is Ca12(Mg5Si9)O32Cl6. Adrianite has the I43d wadalite structure with a = 11.981 Å, V = 1719.8 Å3, and Z = 2, as revealed by electron backscatter diffraction. The calculated density using the measured composition is 3.03 g/cm3. Adrianite is a new secondary mineral in Allende, apparently formed by alkali-halogen metasomatic alteration of primary CAI minerals such as melilite, anorthite, perovskite, and Ti,Al-diopside on the CV chondrite parent asteroid. Formation of secondary Cl-rich minerals sodalite, adrianite, and wadalite during metasomatic alteration of the Allende CAIs suggests that the metasomatic fluids had Cl-rich compositions. The mineral name is in honor of Adrian J. Brearley, mineralogist at the University of New Mexico, U.S.A., in recognition of his many contributions to the understanding of secondary mineralization in chondritic meteorites.
Chi Ma↗
Adrianite, Ca12(Al4Mg3Si7)O32Cl6, a New Cl-rich Silicate Mineral from the Allende Meteorite: An Alteration Phase in a Ca-Al-rich Inclusion
Adrianite (IMA 2014-028), Ca12 (Al4Mg3Si7)O32Cl6, is a new Cl-rich silicate mineral and the Si, Mg analog of wadalite. It occurs with monticellite, grossular, wadalite, and hutcheonite in altered areas along some veins between primary melilite, spinel, and Ti, Al-diopside in a Type B1 FUN (Fractionation and Unidentified Nuclear effects) Ca-Al-rich inclusion (CAI), Egg-3, from the Allende CV3 carbonaceous chondrite. The mean chemical composition of type adrianite by electron probe microanalysis is (wt%) CaO 41.5, SiO2 27.5, Al2O3 12.4, MgO 7.3, Na2O 0.41, Cl 13.0, O=Cl –2.94, total 99.2, giving rise to an empirical formula of (Ca11.69Na0.21) (Al3.85Mg2.88Si7.23) O32Cl5.80. The end-member formula is Ca12 (Mg5Si9) O32Cl6. Adrianite has the I43d wadalite structure with a = 11.981 Å, V = 1719.8 Å3, and Z = 2, as revealed by electron backscatter diffraction. The calculated density using the measured composition is 3.03 g/cm3. Adrianite is a new secondary mineral in Allende, apparently formed by alkali-halogen metasomatic alteration of primary CAI minerals such as melilite, anorthite, perovskite, and Ti,Al-diopside on the CV chondrite parent asteroid. Formation of secondary Cl-rich minerals sodalite, adrianite, and wadalite during metasomatic alteration of the Allende CAIs suggests that the metasomatic fluids had Cl-rich compositions. The mineral name is in honor of Adrian J. Brearley, mineralogist at the University of New Mexico, U.S.A., in recognition of his many contributions to the understanding of secondary mineralization in chondritic meteorites.
Adrianite↗
Crystal Chemistry of Melanite Garnet
This original project resulted in a detailed crystal chemical data map of a titanium rich garnet (melanite) suite that originates from the Crowsnest Volcanics of Alberta Canada. Garnet is typically present during the partial melting of the earth's mantle to produce basalt. Prior studies conducted at Youngstown State University have yielded questions as to the crystal structure of the melanite. In the Studies conducted at Youngstown State University, through the use of single crystal x-ray diffraction, the c-axis appears to be distorted creating a tetragonal crystal instead of the typical cubic crystal of garnets. The micro probe was used on the same suite of titanium rich garnets as used in the single crystal x-ray diffraction. The combination of the single crystal x-ray research and the detailed microprobe research will allow us to determine the exact crystal chemical structure of the melanite garnet. The crystal chemical data was gathered through the utilization of the SX100 Electron Probe Micro Analyzer. Determination of the exact chemical nature may prove useful in modeling the ultramafic source rock responsible for the formation of the titanium rich lunar basalts.
Nguyen, Dawn Marie↗
Photon-scattering cross sections of H2 and He measured with synchrotron radiation
Total (elastic + inelastic) differential photon-scattering cross sections have been measured for H2 gas and for He, using an X-ray beam. Absolute measured cross sections agree with theory within the probable errors. Relative cross sections (normalized to theory at large S) agree to better than 1% with theoretical values calculated from wave functions that include the effect of electron-electron Coulomb correlation, but the data deviate significantly from theoretical independent-particle (e.g., Hartree-Fock) results. The ratios of measured absolute He cross sections to those of H2, at any given S, also agree to better than 1% with theoretical He-to-H2 cross-section ratios computed from correlated wave functions. It appears that photon scattering constitutes a very promising tool for probing electron correlation in light atoms and molecules. The degree of polarization of the synchrotron radiation beam has been measured by rotating the scattering plane about the beam axis; results are compared with theory.
Ice, G. E.↗