The BACH beamline (Beamline for Advanced diCHroism) is an undulator beamline of the Istituto Officina dei Materiali-Consiglio Nazionale delle Ricerche, which operates at Elettra, in close collaboration with Elettra-Sincrotrone Trieste S.C.p.A.. The beamline offers a multi-spectroscopy approach for the investigation of the electronic, chemical, structural, magnetic and dynamical properties of solid surfaces, interfaces, thin films and solid samples in the UV-soft x-ray photon energy range (44-1650 eV) with selectable light polarization (linear horizontal and vertical, circular), high resolving power (20000-6000) and time resolution (70 psec). Each UHV endstation has a UHV connected preparation chamber for sample growth and surface preparations (sputtering, annealing, evaporators for organics and metals, LEED, mass analyser, leak valves for gas exposures...) and a quick UHV connected sample transfer load lock. In the load lock, exposures up to 100 torr of selected gas and sample heating up to 1000 K can be performed.
The experimental setup of the BRANCHA can also combine Laser and Synchrotron Radiation (SR) in order to study the dynamics of the photo-induced excited states of electronic and magnetic systems with pump-probe time-resolved XAS. Elettra Synchrotron radiation source provide radiation pulse widths sufficiently short to investigate dynamic processes in the time between 70 ps up to 0.5 μs. Typically, optical excitation of the sample is done by laser pulses (synchronized to either hybrid or multi bunch SR pulses), and probing is performed by time-delayed synchrotron radiation pulses.
An hemispherical analyser with vertical entrance slit and 2D detector offers the possibility to perform polarisation dependent soft-x ray ARPES and VUV ARPES in the full range of the beamline (44-1650 eV) on in situ prepared samples.
Sample holders for UHV compatible fluorescence yield XAS in liquid environment are available upon preliminary request.
Recently an in-operando soft-x-ray XAS set up has been implemented at BACH to bridge the “pressure gap” between UHV and ambient pressure, based on the confinement of liquids in a cell with a window separating the fluid from the UHV. One of the end-stations has been dedicated to experiments based on electron transfer processes at the solid/liquid interfaces and during photocatalytic or electrochemical reactions. Suitable cells to perform soft x-ray spectroscopy in the presence of liquids were developed: static cells to study the solid/liquid interface of catalysts in the presence of an electrolyte both in total electron yield (TEY) and fluorescence yield (TFY), and an electrochemical flow cell which allows to carry out in situ cyclic voltammetry, electrodeposition on a working electrode (WE) and to study chemical reactions in-operando conditions and under selected applied voltages.
Endstations and experimental techniques
ENDSTATION A:XPS/UPS,VUV and soft x-ray ARPES,RESPES, RES-ARPES, CIS, Photoelectron Diffraction, fast XPS (ms), XAS (TEY,PEY,TFY,PFY),XLD, in remanence XMCD, XES, Time resolved laser pump-probe XAS (ps) 50-100 K to 800 K + UHV Preparation Chamber
ENDSTATION B: in-operando soft-x-ray XAS set up (at the solid/liquid interfaces and during photocatalytic or electrochemical reactions)
BRANCHLINE C: available for user endstations