Glancing incidence telescopes of the kind first described by Wolter have now been physically real... more Glancing incidence telescopes of the kind first described by Wolter have now been physically realized, so that it is now possible to obtain high resolution images of celestial objects at all wavelengths greater than about 3 Å. In this paper we shall describe two such instruments: the GSFC-MSFC X-ray telescope for the Apollo telescope mount uses Wolter type 1 optics and is capable of forming images of the sun in the 8–70 Å region with spatial resolution of the order of one arc second. The GSFC extreme ultraviolet spectroheliometer for OSO H uses type 2 optics and can obtain images of the Sun in spectral lines in the 170–400 Å region with a spatial resolution of about ten arc seconds. Theoretical (ray trace) and laboratory data on these systems will be presented.
Materials Characterization and Optical Probe Techniques: A Critical Review
This is a review of the applications that various core level spectroscopies have in surface analy... more This is a review of the applications that various core level spectroscopies have in surface analysis. Three methods are highlighted, i.e., photoelectron spectroscopy of core level shifts (XPS or ESCA), absorption spectroscopy, and soft X- ray fluorescence. These techniques provide not only elemental analysis at surfaces, but also the chemical state of atoms and molecules in the outermost atomic layers,
... W. NG, AK RAY-CHAUDHURI, S. LIANG, S. SINGH, H. SOLAK, F. CERRINA, 'G. MARGARITO... more ... W. NG, AK RAY-CHAUDHURI, S. LIANG, S. SINGH, H. SOLAK, F. CERRINA, 'G. MARGARITONDO, *L. BRILLSON, tA. ... However, the count rate at this resolution is quite low because of the relatively large emittance of Aladdin, and the signal to noise ratio becomes the limiting ...
ABSTRACT VUV and soft x-ray radiation is being used in a tremendous variety of ways to investigat... more ABSTRACT VUV and soft x-ray radiation is being used in a tremendous variety of ways to investigate the physical and chemical properties of condensed matter, with these including x-ray photoelectron spectroscopy (XPS), x-ray photoelectron diffraction (XPD), x-ray emission spectroscopy (XES), and x-ray magnetic dichroism in all of these experiments using both circular and linear polarization (XMCD and XMLD). Nevertheless, the interaction between soft x-rays and condensed matter is not yet fully understood, especially near strong absorption resonances and for more complex sample morphologies involving multilayers and other nanostructures, leaving several unsolved and interesting problems for both experimentalists and theorists. In particular, much work is presently going on to better understand and utilize these spectroscopies near the absorption edges, including resonant photoemission spectroscopy (RPES) in the valence band, multi-atom resonant photoemission spectroscopy (MARPE) between two core levels, and x-ray magnetic dichroism (XMCD or XMLD) in both x-ray absorption and photoemission. We write a new program which includes all aspects of the classiacal x-ray interaction with the surface and various buried interfaces (e.g. multiple reflections), as well as accurate estimates of photoelectric cross sections and of photoelectron inelastic attenuation lengths in finally determining photoelectron intensities as numerically integrated over depth. Changes in the index of refraction (and thus x-ray attenuation lengths) in passing through any core absorption edges have also been allowed for via experimentally-determined x-ray absorption coefficients and Kramers-Kronig analysis consistent with the off-resonance data of Henke et al. We carry out studies of both total reflection and standing wave effects, with some preliminary results and find out that there is remarkably good agreement between the calculation and experiment on standing wave multilayers as well as free surfaces. These are some first experimental and theoretical results concerning total reflection and standing waves in photoemission that will be expanded in the future to involve both photoemission and more bulk sensitive x-ray emission, as well as measurements on and off core resonances, thus enabling us to more precisely study both free surface and buried-interface properties. Some systems to which this will be applied are interfaces in GMR-related structures, pinning between antiferromagntic and ferromagnetic layers, and various interfaces in oxide-metal magnetic tunnel junctions.
... 1026 UNDERWOOD ET AL. Vol. 224 flares similar to the August 9 event. In this regard, we may a... more ... 1026 UNDERWOOD ET AL. Vol. 224 flares similar to the August 9 event. In this regard, we may ask, in conclusion, how the work reported here relates to other studies of the temperature structure of flare plasmas, and the problem of the plasma evolution in general. Jordan (1976 ...
Proceedings of Spie the International Society For Optical Engineering, 1997
Beamline for metrology of x-ray/EUV optics at the Advanced Light Source. [Proceedings of SPIE 311... more Beamline for metrology of x-ray/EUV optics at the Advanced Light Source. [Proceedings of SPIE 3113, 214 (1997)]. James H. Underwood, Eric M. Gullikson, Masato Koike, Phillip J. Batson. Abstract. We describe a bending magnet ...
We report a novel type of non-destructive method for spectroscopically probing buried nanometer-s... more We report a novel type of non-destructive method for spectroscopically probing buried nanometer-scale interfaces and other nanostructures with soft x-ray standing waves. Strong standing waves with a period of 4.0 nm and an approximately 4 contrast ratio are created above a synthetic multilayer of form [B4C/W]40. Magnetic circular dichroism in photoemission from the 2p and 3p levels of Fe and
This patent describes a spectrometer optical system employed in combination with a source of elec... more This patent describes a spectrometer optical system employed in combination with a source of electromagnetic radiation and reception means. It comprises: a first concave mirror receiving electromagnetic radiation from the source and reflecting the electromagnetic radiation within a first plane; a second concave mirror receiving the electromagnetic radiation reflected from the source and reflecting the electromagnetic radiation to converge in a second plane. The first and second planes being substantially orthogonal relative to each other; a diffraction grating receiving the converging electromagnetic radiation from the source and producing a spectrum for capture by the reception means; and means for rotating the diffraction grating about an axis relative to the diffraction grating.
Glancing incidence telescopes of the kind first described by Wolter have now been physically real... more Glancing incidence telescopes of the kind first described by Wolter have now been physically realized, so that it is now possible to obtain high resolution images of celestial objects at all wavelengths greater than about 3 Å. In this paper we shall describe two such instruments: the GSFC-MSFC X-ray telescope for the Apollo telescope mount uses Wolter type 1 optics and is capable of forming images of the sun in the 8–70 Å region with spatial resolution of the order of one arc second. The GSFC extreme ultraviolet spectroheliometer for OSO H uses type 2 optics and can obtain images of the Sun in spectral lines in the 170–400 Å region with a spatial resolution of about ten arc seconds. Theoretical (ray trace) and laboratory data on these systems will be presented.
Materials Characterization and Optical Probe Techniques: A Critical Review
This is a review of the applications that various core level spectroscopies have in surface analy... more This is a review of the applications that various core level spectroscopies have in surface analysis. Three methods are highlighted, i.e., photoelectron spectroscopy of core level shifts (XPS or ESCA), absorption spectroscopy, and soft X- ray fluorescence. These techniques provide not only elemental analysis at surfaces, but also the chemical state of atoms and molecules in the outermost atomic layers,
... W. NG, AK RAY-CHAUDHURI, S. LIANG, S. SINGH, H. SOLAK, F. CERRINA, 'G. MARGARITO... more ... W. NG, AK RAY-CHAUDHURI, S. LIANG, S. SINGH, H. SOLAK, F. CERRINA, 'G. MARGARITONDO, *L. BRILLSON, tA. ... However, the count rate at this resolution is quite low because of the relatively large emittance of Aladdin, and the signal to noise ratio becomes the limiting ...
ABSTRACT VUV and soft x-ray radiation is being used in a tremendous variety of ways to investigat... more ABSTRACT VUV and soft x-ray radiation is being used in a tremendous variety of ways to investigate the physical and chemical properties of condensed matter, with these including x-ray photoelectron spectroscopy (XPS), x-ray photoelectron diffraction (XPD), x-ray emission spectroscopy (XES), and x-ray magnetic dichroism in all of these experiments using both circular and linear polarization (XMCD and XMLD). Nevertheless, the interaction between soft x-rays and condensed matter is not yet fully understood, especially near strong absorption resonances and for more complex sample morphologies involving multilayers and other nanostructures, leaving several unsolved and interesting problems for both experimentalists and theorists. In particular, much work is presently going on to better understand and utilize these spectroscopies near the absorption edges, including resonant photoemission spectroscopy (RPES) in the valence band, multi-atom resonant photoemission spectroscopy (MARPE) between two core levels, and x-ray magnetic dichroism (XMCD or XMLD) in both x-ray absorption and photoemission. We write a new program which includes all aspects of the classiacal x-ray interaction with the surface and various buried interfaces (e.g. multiple reflections), as well as accurate estimates of photoelectric cross sections and of photoelectron inelastic attenuation lengths in finally determining photoelectron intensities as numerically integrated over depth. Changes in the index of refraction (and thus x-ray attenuation lengths) in passing through any core absorption edges have also been allowed for via experimentally-determined x-ray absorption coefficients and Kramers-Kronig analysis consistent with the off-resonance data of Henke et al. We carry out studies of both total reflection and standing wave effects, with some preliminary results and find out that there is remarkably good agreement between the calculation and experiment on standing wave multilayers as well as free surfaces. These are some first experimental and theoretical results concerning total reflection and standing waves in photoemission that will be expanded in the future to involve both photoemission and more bulk sensitive x-ray emission, as well as measurements on and off core resonances, thus enabling us to more precisely study both free surface and buried-interface properties. Some systems to which this will be applied are interfaces in GMR-related structures, pinning between antiferromagntic and ferromagnetic layers, and various interfaces in oxide-metal magnetic tunnel junctions.
... 1026 UNDERWOOD ET AL. Vol. 224 flares similar to the August 9 event. In this regard, we may a... more ... 1026 UNDERWOOD ET AL. Vol. 224 flares similar to the August 9 event. In this regard, we may ask, in conclusion, how the work reported here relates to other studies of the temperature structure of flare plasmas, and the problem of the plasma evolution in general. Jordan (1976 ...
Proceedings of Spie the International Society For Optical Engineering, 1997
Beamline for metrology of x-ray/EUV optics at the Advanced Light Source. [Proceedings of SPIE 311... more Beamline for metrology of x-ray/EUV optics at the Advanced Light Source. [Proceedings of SPIE 3113, 214 (1997)]. James H. Underwood, Eric M. Gullikson, Masato Koike, Phillip J. Batson. Abstract. We describe a bending magnet ...
We report a novel type of non-destructive method for spectroscopically probing buried nanometer-s... more We report a novel type of non-destructive method for spectroscopically probing buried nanometer-scale interfaces and other nanostructures with soft x-ray standing waves. Strong standing waves with a period of 4.0 nm and an approximately 4 contrast ratio are created above a synthetic multilayer of form [B4C/W]40. Magnetic circular dichroism in photoemission from the 2p and 3p levels of Fe and
This patent describes a spectrometer optical system employed in combination with a source of elec... more This patent describes a spectrometer optical system employed in combination with a source of electromagnetic radiation and reception means. It comprises: a first concave mirror receiving electromagnetic radiation from the source and reflecting the electromagnetic radiation within a first plane; a second concave mirror receiving the electromagnetic radiation reflected from the source and reflecting the electromagnetic radiation to converge in a second plane. The first and second planes being substantially orthogonal relative to each other; a diffraction grating receiving the converging electromagnetic radiation from the source and producing a spectrum for capture by the reception means; and means for rotating the diffraction grating about an axis relative to the diffraction grating.
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Papers by James Underwood