LowDosePES
Low Dose Photoelectron Spectroscopy at PM4
This instrument is dedicated to photoelectron spectroscopy studies at low irradiation doses. Thanks to a fast chopper, the sample is only reached by a single bunch (carrying about two orders of magnitude lower flux than the full multibunch train). Measurements are still efficient thanks to the high transmission of an ArTOF analyser. The wide angle acceptance of the latter also allows angular-resolved photoemission experiments without need for sample rotation. Moreover, a synchronized laser system makes possible excited-state characterization and pump-probe studies with tens of ps resolution.
Selected Applications:- wide k-range 3D band structure mapping of radiation-sensitive and/or inhomogeneous samples at fixed sample/analyser geometry
- real-time (seconds to days) evolution of valence & core photoelectron spectra
- ultrafast (picoseconds to milliseconds) dynamics in valence & core photoelectron spectra following ultrafast optical excitation
- core level resonant photoelectron spectroscopy
- determination of the occupied electronic structure and of molecular orientation by x-ray absorption spectroscopy at different incidence angles
Methods
ARPES, UPS, XPS, XPD, Time-resolved PES, Time-resolved absorption, NEXAFS
Remote access
depends on experiment - please discuss with Instrument Scientist
| Beamline data | |
|---|---|
| Energy range | 20 - 2000 eV |
| Energy resolution | 6,000 at 400 eV |
| Flux | 1e9 - 1e10 phot/s |
| Polarisation | horizontal |
| Focus size (hor. x vert.) | down to 0.1 mm x 0.1 mm |
| Phone | +49 30 8062 14713 |
| More details | PM4 |
| Station data | |
| Temperature range | 20-500 K by resistive heating; up to ~1200 / 1700 K long-term / flashing by electron bombardment; direct current heating also possible |
| Pressure range | Base pressure within <5x10^-10 and 3x10^-9 mbar. With possibility to dose selected gases. |
| Detector | Scienta ArTOF-10k electron energy analyzer |
| Manipulators | 3 sample stages: one 6-axis stage with l-N2/l-He cooling & resistive heating; one 4-axis stage with resistive, direct and electron bombardment heating; one extra 4-axis stage; all stages with sample current readout |
| Sample holder compatibility |
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| Additional equipment | • Top preparation chamber: clean sample preparation - MCP LEED, mass spectrometer, many free ports
• Side preparation chamber for non-organic samples – storage space for 4 samples, of which 2 heatable by resistive heating up to 1000 K or direct heating and 2 heatable by electron bombardment up to 1600 K and coolable by l-N2, sputter gun, gas inlet, mass spectrometer, several free ports • Second side preparation chamber for non-organic samples – storage space for 5 samples, of which 1 heatable by resistive heating up to 900 K, several free ports • Side preparation chamber for organic samples - quartz microbalance, storage space for 6 samples, several free ports for replaceable evaporators etc • Synchronized optical laser: 1030, 515 or 343 nm wavelength, >330 fs pulse duration, tuneable repetition rate up to 1.25 MHz |
The LowDosePES end-station is permanently installed at the PM4 dipole beamline.
It is equipped with an angle-resolved time-of-flight (ArTOF) spectrometer, featuring high transmission and wide angular acceptance.
Thanks to the high transmission of the ArTOF, faster acquisition times and equally reduced dose rates can be achieved with respect to a hemispherical analyzer, thus making possible photoelectron spectroscopy investigations of materials that usually suffer from radiation damage.
When further considering its wide angular acceptance, the ArTOF results particularly suitable to track changes in the sample electronic structure as a function of additional parameters, such as gas exposure, temperature or delay after excitation from an optical pump.
Since the ArTOF needs a pulsed source with repetition rate not exceeding few MHz, a fast mechanical chopper is installed at the intermediate focus of the beamline enabling permanent access to 1.25 MHz -spaced X-ray bunches, not only during single-bunch operation of the storage ring, but also during the more common hybrid operation mode.
When slowed down, the chopper no longer intercepts the beam, and the full filling pattern is delivered to the end-station. This possibility can be used for x-ray absorption spectroscopy measurements in total electron yield.
The end-station has access to a synchronized, ultrafast (pulse length >330 fs), high repetition rate (up to 1.25 MHz), infrared (1030 nm) laser - and its second to third harmonics - for time-resolved laser-pump / x-ray-probe photoemission measurements.
Remote Access Details
Beamline and end-station controls can be operated remotely to a very large extent. While the physical presence of a part of the experimental team is required for sample handling, additional members of the team can be enabled for remote access to the experimental controls.
Upgrades planned for 2022
- Additional hemispherical electron energy analyzer as replacement for the Scienta SES-100 currently out-of-order