[en] A grazing-incidence grating spectrometer has been used for the investigation of the undulator radiation from beamline 411 at MAX-lab. The direct detection of undulator light is expected to obtain the information of the quality of the undulator. Regular undulator radiation and some higher harmonics were observed. The effects of electronic beam coupling and Landau cavities have been studied. The experiment presents an easy and quick method to characterize the undulator radiation before the permanent monochromator is installed. (author)

[en] Complete text of publication follows. The investigation of double differential cross sections of photon induced Auger electrons provides very sensitive method for studying the rearrangement process, especially when the angular correlation between photo- and Auger electrons is also studied. Such type of measurements could reveal a new aspect in studying the electron-electron, hole-electron and photoelectron - Auger electron interactions. It enables one to separate the overlapping Auger lines belonging to different initial holes. The traditional coincidence measurement is very time consuming and causes serious calibration problems. In order to overcome these experimental difficulties a new electron-spectrometer (ESA-22) was developed in ATOMKI, Debrecen in cooperation with the Electron spectroscopy group of University of Oulu, Finland. The analyzer consists of a spherical and a cylindrical part. It is very similar to the ESA-21 analyzer. The main differences is that the focal ring can be set different diameters thus either a series of channel detectors can be used to detect the electrons at different angles or a position sensitive channel plate can be applied for simultaneous angular recording of electrons. Furthermore the outer sphere and cylinder are cut into two parts so the spectrometer is capable to analyze two independent angularly resolved electron spectra (in the 0 deg - 180 deg region) at different energy regions, simultaneously. A special electronic control and data handling electronics and software was worked out to control the analyzer. The first results were presented in. In the last year the ESA-22 electron-spectrometer was transported to the I411 beam line of MAX-II synchrotron in Lund, Sweden. The advanced properties of the spectrometer was investigated by measuring coincidences between the photoelectrons originated from the Ar L₃ subshell and the Ar Auger electrons in the 203-207 eV energy region. Fig. 1 shows the single and the coincidence spectra. It is clearly seen that the overlapping Auger lines belonging to the L₂ and L₃ initial states can be separated with the coincidence condition. This high efficiency coincidence measurement opens a new way to investigate the ionization and rearrangement process. (author)

[en] We report on the characteristics and first results from the soft X-ray beam line I411, based on an undulator at the third generation synchrotron facility MAX II, Sweden. The beam line is designed for high-resolution, angle-resolved electron spectroscopy on gases, liquids and solids. Main components are the modified SX700 monochromator and the end station, both of which were previously used at beam line 51 at MAX I. The end station is equipped with a rotatable SES-200 hemispherical electron-analyser. Before the end station, a one-metre section is reserved for exchangeable experimental set-ups. The usable photon energy range is 50-1500 eV and the photon flux is two orders of magnitudes higher compared to beam line 51. At 400 eV a resolving power of about 5700 in the first order of the monochromator grating could be obtained. In gas phase, a total electron energy resolution of 16 meV has been achieved. Detailed results on the undulator performance, flux, photon and electron energy resolution as well as some technical details are presented here. As an example of the capabilities of the beam line I411, we present the fully vibrationally resolved Auger resonant Raman electron spectrum of gas-phase N₂

[en] Earlier a preliminary paper was presented on the coincidence between photoelectrons and Auger electrons. Recently the experimental investigation has been completed. The Ar L₂₃MM Auger electrons were measured in the 199-208.5 eV energy range in coincidence with the 2p_1/2, 2p_3/2 photoelectrons at 440 eV photon impact. (R.P.)

[en] Full text: Dipole approximation has often been used successfully to describe the angular distribution of photoelectrons and also to evaluate the experimental angular distribution results. The validity of the dipole approximation comes from the dominance of the dipole interaction at low photon energies (hv → 5 keV). Until recently the contribution of the higher order multipole components were assumed to be negligible although Wuilleumier and Krause observed nondipole effects in the 1-2 keV photon energy range already almost 30 years ago. Recently, the nondipole effects at low photon energies have been intensively studied both theoretically and experimentally. The angular distributions of the 5s and 5p photoelectrons of xenon were measured with linearly polarized light in the 100- 200 eV photon energy range. The experiment was done out of so called dipole plane in order to obtain information also about non-dipole angular distribution parameters γ and δ. The experimentally determined angular distribution parameters were compared with theoretical values obtained from the recent calculations based on the relativistic random-phase approximation. The results show that the nondipole angular distribution parameters are very sensitive probes of multielectron correlation

[en] The angular distribution of the 5s photoelectrons of xenon was measured with linearly polarized light in the 90-225 eV photon energy range in order to determine the dipole (β) and nondipole (δ and γ) parameters. The measurements were carried out at the beam line I411 on the third generation MAX-II storage ring in the Max-Lab, in Lund, Sweden. Emitted electrons were detected by 20 channeltrons using ESA-22 electron spectrometer. The relative energy resolution of the analyzer was set to ΔE/E = 2.4 x 10^-3. (R.P.)

[en] Many-electron effects associated with high-lying Rydberg states in the final state of the Ar 2p^-14s→3s¹3p⁵(³P)4s resonant Auger transitions result in numerous line components in the experimental spectrum. Taking advantage of the cascade process we study the quasi-continuum features of the 3s¹3p⁵(³P)4s Auger peaks with the aid of second-step Auger spectra. We discuss the lineshape of the second-step spectra which characteristically consist of very narrow peaks. We also describe model calculations which have been carried out by including the mixing of the configurations using the multiconfiguration Dirac-Fock method. They are found to reproduce the main features of the 3s¹3p⁵(³P)4s peaks reasonably well. (author)

[en] We report a high-resolution coincident experiment between the Ar 2p_1/2 and 2p_3/2 photoelectrons and subsequently emitted L₂₃-M₂₃M₂₃ Auger electrons, where the 2p photoelectrons were ionized far above the threshold. We demonstrate the applicability of the coincidence method when separating the different ionization and decay channels even in the case of strongly overlapping peaks. The measurement was carried out with a new high-energy-resolution electrostatic analyzer that is capable of recording the single and coincidence spectra at large range of emission angles simultaneously. An anomalous value was found for the ²P_3/2-(³P₀₁₂/¹D₂) intensity ratio in the 2p_3/2 coincidence spectrum, while all the other relative intensities are in good agreement with the previously published data. The possible reasons for the difference are discussed

[en] High-resolution Cl 2p^-1 photoelectron (PES) and Cl 2p^-1→3pπ^-2 normal Auger electron spectra (AES) have been measured using different photon energies. The PES and AES have been fitted simultaneously taking vibrational and electronic lifetime-interference terms into account. Detailed results are presented for the Cl 2p^-1→3pπ^-2 normal Auger transitions. The equilibrium distances, vibrational energies, and anharmonicities for the ¹Σ⁺, ¹Δ, and ³Σ^- final states are derived from the intensity distribution of the vibrational substates. The relative intensities for the different Cl 2p^-1→3pπ^-2 normal Auger transitions are also given. In addition to the Cl 2p^-1→3pπ^-2 transitions, some fine structures are observed that show a photon energy dependence. These structures are assigned to decays of doubly excited or shake-up/off states

[en] The angular distribution of the Xe 5s photoelectrons was measured in the 90-225 eV photon energy range using linearly polarized synchrotron radiation. The experimentally determined angular distribution parameters were compared with theoretical values obtained from calculations based on the random-phase approximation and the time-dependent density-functional theory. Experiment shows that the dipole (β) and nondipole (γ) parameters vary strongly as a function of the photon energy, in accordance with calculations that account for the interchannel coupling. Nondipole effects observed clearly in experiment confirm the role of multielectron correlation in describing the 5s photoionization of Xe far from the ionization threshold