Spatial resolution tests were performed on beamline 1.4.4 at the Advanced Light Source in Berkeley, CA, USA, a third-generation synchrotron light source. This beamline couples the high-brightness synchrotron source to a Thermo-Electron Continumicrom XL infrared microscope. Two types of resolution tests were performed in both the mid-IR and near-IR. The results are compared with a diffraction-limited spot size theory. At shorter near-IR wavelengths the experimental results begin to deviate from diffraction-limited so a combined diffraction-limit and electron-beam-source-size model is employed. This description shows how the physical electron beam size of the synchrotron source begins to dominate the focused spot size at higher energies. The transition from diffraction-limited to electron-beam-size-limited performance is a function of storage-ring parameters and the optical demagnification within the beamline and microscope optics. The discussion includes how different facilities, beamlines and microscopes will affect the achievable spatial resolution. As synchrotron light sources and other next-generation accelerators such as energy-recovery LINACs and free-electron lasers achieve smaller beam emittances, beta-functions and/or energy spreads, diffraction-limited performance can continue to higher-energy beams, perhaps ultimately into the extreme ultraviolet.

At the ALS we have been testing out Thermo-Electron’s newest infrared imaging system, the Continuum XL microscope. This microscope is equiped with a 32-element MCT (16 × 2) array which allows rapid infrared imaging with fixed step sizes. The microscope also has a conventional single element MCT-A, which can be swapped for an MCT-B, or InSb detectors. This microscope is installed on ALS Beamline 1.4.4 where the synchrotron source provides high brightness for the single element detectors. We present comparisons of the measured spatial resolutions available with each of these detector types for globar and synchrotron sources as a function of wavelength and optical configuration. We find that the synchrotron retains its superiority for ultimate spatial resolution and signal-to-noise, while the array detection system is fast and convenient for surveying larger regions of a sample. Therefore in practice we use the array system for initial infrared images which allow us to find the regions of interest where we ‘zoom in’ using the synchrotron source.

Absolute photoionization cross sections for Kr{sup 3+} were measured in the energy range 39.05-143.2 eV for single ionization and 120.6-137.7 eV for double ionization. For comparison, an electron-impact single-ionization measurement was made in the energy range 43.1-179.1 eV and normalized to previously published absolute measurements. The Flexible Atomic Code and Cowan atomic structure codes were used to calculate energy levels, excitation energies and oscillator strengths for 3d{yields}np, 3d{yields}nf, and 4s{yields}np autoionizing transitions from the ground and metastable states. From the single-photoionization measurements, ionization thresholds of the {sup 2}P{sup o}{sub 3/2}, {sup 2}D{sup o}{sub 5/2} metastable states and {sup 4}S{sup o}{sub 3/2} ground state were measured to be 46.62{+-}0.02, 48.59{+-}0.01, and 50.70{+-}0.02 eV, nearly 2 eV lower than National Institute of Standards and Technology tabulated values. Within the experimental uncertainty, oscillator strengths determined from the photoionization measurements are in agreement with both calculations. Excitation-autoionization and resonant-excitation double-autoionization features are evident in the electron-impact ionization cross section.

Absolute photoionization cross sections for Kr5+ were measured in the photon energy range 74-175 eV using synchrotron radiation. For comparison, a detailed energy scan of the electron-impact ionization cross section was made in the same energy range and normalized to previously published absolute measurements. The Flexible Atomic Code and Cowan atomic structure code were used to calculate energy levels, excitation energies, and oscillator strengths for 3d -> np, 3d -> nf, and 4s -> np autoionizing transitions from the ground and metastable states. Within the experimental uncertainty, oscillator strengths determined from the photoionization measurements are in agreement with both calculations. Excitation-autoionization and resonant excitation-double-autoionization features are evident in the electron-impact ionization cross section.

Absolute photoionization cross sections for Kr3+ were measured in the energy range 39.05-143.2 eV for single ionization and 120.6-137.7 eV for double ionization. For comparison, an electron-impact single-ionization measurement was made in the energy range 43.1-179.1 eV and normalized to previously published absolute measurements. The Flexible Atomic Code and Cowan atomic structure codes were used to calculate energy levels, excitation energies and oscillator strengths for 3d -> np, 3d -> nf, and 4s -> np autoionizing transitions from the ground and metastable states. From the single-photoionization measurements, ionization thresholds of the P-2(3/2)o, D-2(5/2)o metastable states and S-4(3/2)o ground state were measured to be 46.62 +/- 0.02, 48.59 +/- 0.01, and 50.70 +/- 0.02 eV, nearly 2 eV lower than National Institute of Standards and Technology tabulated values. Within the experimental uncertainty, oscillator strengths determined from the photoionization measurements are in agreement with both calculations. Excitation-autoionization and resonant-excitation double-autoionization features are evident in the electron-impact ionization cross section.