Grazing Incidence Monochromator Research Articles

C/Si multilayer mirrors for the 25–30-nm wavelength region

We report a new material combination, C/Si, for normal-incidence multilayer mirrors in the wavelength region 25-30 nm. The multilayers, fabricated by ion-beam-sputtering deposition, were characterized by near-normal-incidence reflectance measurements by using a discharge source and a grazing-incidence monochromator. The highest measured near-normal-incidence reflectance was R = 23% (25.6 nm), R = 20% (28.3 nm), R = 25% (30.4 nm) at incident angles of 10 degrees , 12 degrees , and 4 degrees , respectively. The multilayers were also characterized by transmission electron microscopy, which revealed sharp layer interfaces and low interfacial roughness.

Application of high-resolution, high-sensitivity spectrometry in the extreme ultraviolet wavelength range for diagnostics of single and double electron capture processes in He2++He and Ar8++He collisions

We have applied a new, more efficient diagnostic technique for studies of extreme ultraviolet (EUV) radiation from multicharged ions interacting with He gas. Following single and double electron capture and one electron capture plus target-ion excitation in He2++He and Ar8++He collisions, the subsequent emitted EUV photons are analyzed with a high-resolution 2.2 m grazing incidence monochromator in conjunction with a new type of glass capillary converter (GCC) specifically designed for the EUV wavelength region. This new optical device images a horizontal cylindrical ion beam segment onto the vertical entrance slit of the monochromator. With this new imaging technique a spectral intensity enhancement of about 10 has been achieved over a distance of about 60 cm. By further optimizing this method an enhancement of the flux density of EUV radiation of about 20–30 is expected. As prototype examples, new advanced EUV spectra arising from He2++He and Ar8++He collisions are presented and discussed.

Development of a Tunable UV Laser System Synchronizing Precisely with Synchrotron Radiation Pulses from UVSOR

A mode-locked Ti:sapphire laser is made to oscillate at the frequency of the UVSOR storage ring, 90.115 MHz, in a multi-bunch operation mode. The third harmonic of the laser is available in the wavelength range 243-280 nm. Synchrotron radiation from an undulator is monochromated by a grazing-incidence monochromator and introduced coaxially with the laser. The temporal profile of the photon pulses is monitored in situ by a luminescing substance/photomultiplier combination. The delay timing between the laser and synchrotron radiation can be changed from 0 to 11 ns by adjusting an electronic module that provides phase-locked loop stabilization of the laser pulse. The reliability and feasibility of this laser-synchrotron radiation combination technique are demonstrated by applying pump-probe experiments to two physical systems. The first system is photodissociation of iodomethane (CHA) with a laser photon, followed by photoionization of I and CH3 fragments with synchrotron radiation. The second, two-photon ionization of He atoms, is studied as the prototype of a time-resolved experiment. The He+ signal counts as a function of the laser-synchrotron radiation delay are found to be enhanced in a narrow time window, which can be interpreted in terms of a short lifetime of the resonant state, He*(1s2p 1P), produced by primary synchrotron radiation excitation.

Application of new spectroscopic technique for the study of interaction of multicharged ions with gaseous targets in the extreme ultraviolet

A new optical technique for the extreme ultraviolet (EUV) spectral region based on glass capillary converters has been tested for studies of highly charged ion collision processes, plasma diagnostics and synchrotron radiation applications. Specifically a complex glass capillary converter system has been utilized in conjunction with a high resolution 2.2m grazing incidence monochromator to record EUV (10-100 nm) projectile and target spectra following multicharged ion collisions with He, leading to an enhancement of detected EUV photon flux between 10 and 30.

Design of a Holographically Recorded Plane Grating with a Varied Line Spacing for a Soft X-ray Grazing-Incidence Monochromator

A new design concept is presented for a plane grating with a varied line spacing for the Monk-Gillieson mounting monochromator. A light path function including both a spherical mirror and a varied-line-spacing grating is defined to optimize groove parameters. Aspheric wavefront recording optics are utilized to fabricate a grating holographically. Ray-tracing results show that the varied-line-spacing grating eliminates aberrations significantly and affords a high resolving power as a total optical system of a soft X-ray grazing-incidence monochromator. The effects of errors in recording parameters and in the radius of the spherical mirror are described, and possible ways to compensate for these errors are discussed.

Resonant Photoemission from Complex Cuprates and Nickelates

Synchrotron-excited resonant-photoemission measurements at rare-earth 4d --> 4f and transition-metal 3p --> 3d thresholds have been carried out using a variety of complex cuprates and nickelates on stations 6.1 (grazing-incidence monochromator) and 6.2 (toroidal-grating monochromator) at the SRS CLRC Daresbury Laboratory. The systems studied are Nd(2)Ni(1 - x)Cu(x)O(4), La(2 - x)Sr(x)Ni(1- y)Fe(y)O(4 + delta) and Bi(2)Sr(2)Ca(1 - x)Y(x)Cu(2)O(8 + delta). A combination of EDC and constant-initial-state data is used to examine the 4f and 3d contributions to the valence-band density of states and their binding-energy positions relative to the Fermi energy. This allows the study of the valence states of the transition-metal ions and their modulation on doping. For La(2 - x)Sr(x)Ni(1 - y)Fe(y)O(4 + delta), this approach is used to infer a valence state of >/= 3.0 for Fe. In the case of Bi(2)Sr(2)Ca(1 - x)Y(x)Cu(2)O(8 + delta), the effect of Cu valence modulation on the 3p resonance is observed as x is varied. This is discussed in the light of controversy surrounding shifts in core-level photoemission with doping for this system.

A Brief Review of the History and Use of the Daresbury `Miyake' Monochromator for Surface Science

This paper celebrates the 21st anniversary of the plane-grating grazing-incidence monochromator, designed at Daresbury in 1974 and in almost continuous operation ever since. The order-sorting principles [Miyake, Kato & Yamashita (1969). Sci. Light (Tokyo), 18, 39-56] are described, along with the detail of the instrument's design, followed by the history of its use on three synchrotron radiation sources (NINA, TANTALUS and SRS). A selection of scientific highlights at the SRS is given, taken from some of the experimental programmes in which the author was involved, concentrating on tunable photon-energy photoemission studies of metallic alloys. Finally, the future prospects for vacuum UV spectroscopy for surface science are briefly discussed.

Variable groove-spaced grating monochromator for soft x-ray emission spectroscopy at CAMD/LSU

A grazing incidence monochromator, equipped with a variable groove-spaced plane grating, has been commissioned recently at the Center for Advanced Microstructures and Devices, at Louisiana State University. This high-throughput and moderate-resolution monochromator is used as an excitation source for a soft x-ray emission spectrometer.

High-resolution grazing incidence plane grating monochromator for undulator radiation

A grazing incidence monochromator consisting of a spherical mirror, a varied spacing plane grating, movable plane mirror, and a fixed exit slit has been designed by means of a hybrid design method which takes advantage of both the ray-tracing and analytic methods. In the design, higher-order suppression and on-blaze feature were also taken into consideration. A spectral resolving power of ∼30 000–70 000 is expected for the monochromator over a wavelength range of 0.5–10 nm when used on an undulator beamline at the Advanced Light Source.

Fourth-order optical aberrations and phase-space transformation for reflection and diffraction optics

One can derive fourth-order optical ray deviations for a mirror or grating from the optical path function by using the analytical code REDUCE. Some of the aberrations are discussed for normal-incidence and grazing-incidence monochromators. The nonlinear transformation of light from the source to the image plane of a mirror or grating is represented by a transformation matrix. The optical properties of a combination of several optical elements are given by the product of the matrices of the individual optical elements. The matrix elements can be interpreted as optical aberrations. A program has been written that optimizes a complete beam line with respect to various optical aberrations by minimizing an appropriate cost function that is built from a weighted sum of the matrix elements.

Surface normal rotation: a new technique for grazing-incidence monochromators

A class of fixed-slit monochromator that scans wavelength over a broad region using a grazing-incidence diffraction grating that rotates about its surface normal is described.

A 2-m grazing incidence monochromator with a silicon-carbide-based master grating for undulator radiation

Performance of a 2-m grazing incidence vacuum ultraviolet (VUV)/soft x-ray monochromator was evaluated with silicon-carbide-based master grating of 1200 lines/mm groove density that was newly developed for use of undulator radiation. Incident power density on the grating surface was as high as 120 mW/mm2. Surface observation of the grating after the test operation showed that the periodic structure and reflective surface of the grooves were well preserved, except for slight degradation of the groove edges, even though no active cooling system was equipped. Photon flux was of the order of 1012 photons/s. Efficiency of second-order diffraction relative to the first-order diffraction was 20%–50%. Resolving power of 2200 was achieved at 244.4 eV for 5-μm exit slit width.

High resolution and symmetry resolved core-level spectroscopy using soft x-ray undulator (invited)

The performance of a soft x-ray undulator beamline equipped with a 10 m grazing incidence monochromator is described. Several experimental results are presented to exemplify the good performance. The decomposition of photoabsorption spectra of CO and O2 into their component molecular symmetries has been achieved by our new experimental technique of angle-resolved photoion spectroscopy. Two Rydberg series converging to the K-shell ionization limits of O2 have been revealed in a high resolution spectrum.

Current status of 10-m GIM for soft x-ray undulator at the Photon Factory

The current performance of a 10-m grazing incidence monochromator (GIM) is described. A resolution of 51, 95, and 220 meV (FWHM) has been achieved at 287, 401, and 867 eV, respectively, inferred from the linewidths for the K-shell resonances of gaseous CO, N2, and Ne. A photon flux of ≂1012 photons/s is obtainable at the first harmonic of undulator radiation with a 1200-ℓ /mm grating and 50-μm slit openings, which correspond to Δλ=0.04 Å.

Design and application of a varied-space plane grating monochromator for synchrotron radiation

A grazing-incidence monochromator was constructed for a soft-X-ray beam line at the Photon Factory. The monochromator utilizes the self-focusing property of a plane grating with varied-space grooves. A grating with a nominal groove density of 2400 gr/mm covers the spectral range of 0.7–10 nm, and a grating of 800 gr/mm covers 8–30 nm. The resolution of the monochromator was estimated experimentally to be 1200 at 5 nm. A grazing-incidence bent mirror refocuses the outgoing beam onto the experimental area and a mirror assembly suppresses the higher-order harmonics. The monochromator system has been used in practice for soft-X-ray spectroscopy by taking advantage of the broad spectral coverage, high resolution, and high throughput.

Multilayer coated concave diffraction grating resolution and efficiency in the extreme ultraviolet

Recent advances in multilayer structures for the extreme ultraviolet now make it possible to construct diffraction gratings in the wavelength range below 350 A, which can be used for precision measurements using normal incidence spectrometers. We report results from two such gratings, one with conventionally ruled blazed facets and the other with a holographically ruled sinusoidal surface. Both gratings are 1 m in radius, 1200 lines/mm coated with a molybdenum-silicon multilayer for use in the 150 A wavelength region. A 1 m normal incidence spectrometer with a Garton flash tube source and a film detector was used to test the spectral resolution. Relative efficiency measurements were obtained by comparison to spectra produced by an osmium coated grating. Emission lines in the wavelength region of interest (characteristic of the source) are easily detected and well resolved with both multilayer coated gratings. Quantitative efficiency measurements were obtained using a Penning source coupled to a 1 m grazing incidence monochromator and an imaging photon counting detector.

The Vibrational Fine Structure of Chemisorbed C2H4 Molecules in the (1s-1, π*) State

The fine structure of C2H4 molecules in the (1s-1, π*) state is resolved using a plane grating ellipsoidal mirror grazing incidence monochromator at the storage ring BESSY. Two vibrational series can be identified, assigned to C-C and C-H vibrations. The natural line width of the (1s-1, π*) state was found to be 160 meV for condensed C2H4 multilayers. For submonolayers of C2H4 molecules on Ag(100) and Cu(100) this value was found to increase to 280 and 700 meV respectively. A shift to lower energies of the ground state transition is observed for the adsorbed molecules with respect to the multilayer case.

High resolution photoabsorption spectroscopy at the carbonK-Edge

Using plane grating, ellipsoidal mirror, grazing incidence monochromators at the storage ring BESSY, a resolution of ≦ 150meV was achieved for a photon energy of 285 eV. This high energy resolution considerably extends the range of possible studies using core level Spectroscopy. Some of the new opportunities are illustrated at the CK edge by resolving the vibrational fine structure of condensed C2H4 multilayers in the (1s−1, π*) state by means of photoabsorption spectroscopy. For the sake of comparison with other high resolution instruments, the vibrational fine structure of condensed N2 multilayers at the NK edge (∼ 400eV) was also measured, yielding a resolving power of 3000.

Photoemission studies of Si(100) oxidation process (abstract)

Photoemission spectroscopy using synchrotron radiation is a powerful tool to investigate electronic states of solid surfaces. In the present study, the oxidation process of the Si(100) surface has been extensively examined. Experiments were carried out with soft x-rays monochromatized by the grazing incidence monochromator,1 at beamline 8A at the Photon Factory. The energy resolution, including both the electron energy analyzer (a double-pass type CMA) and the monochromator, was estimated from the Au Fermi edge. The Au foil was sputter cleaned by Ar ions. For the photon energy between 40 and 200 eV, the resolution is about 0.3 eV with electron pass energy of 10 eV and monochromator exit slit width of 10 μm. The oxidation process of a Si(100) surface has been examined in situ at the base pressure of 5×10−8 Pa. The Si(100) clean surface is obtained by repeating Ar ion sputtering and annealing. We have measured the Si 2p photoelectron spectra of the Si(100) surface exposed to oxygen. At the early stage of 20–1000 ℓ oxygen exposure at room temperature, outermost Si atoms are partially oxidized and an energy shift of 1–2 eV is observed. The oxidation proceeds much faster when the surface is heated at 300–400 °C during oxygen exposure. In this case, three intermediary components (SiOx x<2) and SiO2 are detected. By further oxidation (104 ℓ oxygen exposure) at 700 °C, a thin SiO2 layer is formed. In addition, valence band and Si L2,3 XANES spectra have been taken for the surface. The results support the oxidation process clarified by the present method.

Grazing-incidence monochromator for the 15–800 Å wavelength range at the storage ring VEPP-2M

A new Rowland monochromator with a fixed output slit, which operates according to the grazing-incidence scheme, is described. The device is notable for the capability to change the Rowland radius within 1–3 m. The monochromator was tested using synchrotron radiation from the storage ring VEPP-2M.