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Third-generation synchrotron radiation light sources provide partially coherent radiation. Certain topics in the optical design of beam lines and monochromators can be studied with electric-field distributions only rather than with intensity distributions of the light source. The radiation characteristics of a dipole or an undulator can be represented by a two-dimensional complex-electric-field distribution at a distance of several meters from the insertion device center. A method is described that transforms this field distribution through a complete beam line (consisting of mirrors and gratings) to the sample plane. Diffraction at apertures can be modeled and Stokes parameters can be evaluated. The derivation of the equations was performed with the algebraic code REDUCE. A comparison with the brightness formalism is provided. Key words: Synchrotron radiation, ray tracing, Stokes parameters, diffraction.

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. Key words: Optical aberrations, ray tracing, phase-space transformation.

Vibrational progressions due to the a 3Π, a’ 3Σ+, d 3Δ, and e 3Σ- states of CO in Ar, Kr, and Xe crystals are observed in absorption. Two groups of phonon sidebands separated from the zero phonon lines by about 4 and 8 meV for the a’ 3Σ+ and d 3Δ states are attributed to librations and to localized phonons. The broad absorption bands, the even broader emission bands, and the large Stoke shift of the a 3Π transition are treated in terms of a configuration coordinate model by a momentum analysis. A quadratic coupling has to be invoked with relaxation energies in the excited states increasing from 14 meV for Ar to 95 meV for Xe and with relaxation energies in the ground state increasing from 29 meV for Ar up to 1278 meV for Xe. The changes of the configuration coordinate of 0.2 to 1.5 Å are also discussed with the help of two pair potential models. [ABSTRACT FROM AUTHOR]

Infrared emission due to W 3Δu (v’=4) → A 3Σ+u (v‘=1, 2) and B’ 3Σ-u (v’=6) → B 3Πg (v‘=1, 2) transitions of N2 molecules isolated in Kr matrices has been observed. The bottlenecks for radiationless relaxation which allow for a competition by these rather slow radiative transitions are identified by selectively populating individual vibrational levels in the vibrational progression of the A 3Σ+u, B 3Πg, a 1Πg, and w 1Δu states. [ABSTRACT FROM AUTHOR]

Photon beams of 99 eV energy carrying orbital angular momentum (OAM) have been observed in the 2nd harmonic off-axis radiation of a helical undulator at the 3rd generation synchrotron radiation light source BESSY II. For detection, the OAM carrying photon beam was superimposed with a reference beam without OAM. The interference pattern, a spiral intensity distribution, was recorded in a plane perpendicular to the propagation direction. The orientation of the observed spiral structure is related to the helicity of the undulator radiation. Excellent agreement between measurements and simulations has been found. [ABSTRACT FROM AUTHOR]

Describes the design goals and the performance data for the exactly focusing spherical grating monochromator at BESSY which is installed on a crossed field undulator for circularly polarized undulator radiation. Description of the beamline; Principle of operation; Measured performance of the instrument.

Describes the transformation of ray coordinates through a complete beamline via single matrix. Application of the transformation matrix either for conventional ray tracing or for phase space transformation; Focus on an optimization program that minimizes a weighted sum of the matrix elements; Development of an approach for the description of beamline optics.

The first experimental results from a double undulator with crossed magnetic fields for producing circularly polarized synchrotron radiation in the vacuum ultraviolet-soft x-ray range are presented. The observed variation of the extent of circularly polarized radiation with photon energy is discussed. A strong dependence of the state and degree of polarization on the exact details of the tuning of the two undulators and the monochromator is observed. This probably accounts for the measured degree of polarization being smaller than theoretically expected. [ABSTRACT FROM AUTHOR]

Excitation spectra of Ar crystals doubly doped with O2 and CO show the a 3Π, a’ 3∑+, d 3Δ, e 3∑-, A 1Π vibrational progressions of CO as well as the Schumann Runge bands ( B 3∑-u) and the following dissociation continuum of O2. In emission the Cameron bands (a 3Π) of CO and the Herzberg bands C 3Δu of O2 have been observed. No electronic energy transfer from CO to O2 or vice versa occurs. This rules out an intramolecular V–E conversion of high vibrational quanta (v=32) in the electronic ground state of CO to the a 3Π (v=3) state of CO and subsequent electronic energy transfer to O2 in the recently reported IR-induced UV-visible fluorescence in matrix-isolated CO thus supporting the other suggested intermolecular V–E and V–V transfer routes. [ABSTRACT FROM AUTHOR]

Describes the construction of two types of monochromators for use on the planned soft x-ray undulator U49 of the BESSY II storage ring. Design goal and boundary conditions; Plane grating monochromator beamline; Spherical grating monochromator beamline.