Performance and characterization of the FinEstBeAMS beamline at the MAX IV Laboratory.

FinEstBeAMS (Finnish-Estonian Beamline for Atmospheric and Materials Sciences) is a multidisciplinary beamline constructed at the 1.5 GeV storage ring of the MAX IV synchrotron facility in Lund, Sweden. The beamline covers an extremely wide photon energy range, 4.5-1300 eV, by utilizing a single elliptically polarizing undulator as a radiation source and a single grazing-incidence plane grating monochromator to disperse the radiation. At photon energies below 70 eV the beamline operation relies on the use of optical and thin-film filters to remove higher-order components from the monochromated radiation. This paper discusses the performance of the beamline, examining such characteristics as the quality of the gratings, photon energy calibration, photon energy resolution, available photon flux, polarization quality and focal spot size.

Gas-phase endstation of electron, ion and coincidence spectroscopies for diluted samples at the FinEstBeAMS beamline of the MAX†IV 1.5†GeV storage ring.

Since spring 2019 an experimental setup consisting of an electron spectrometer and an ion time-of-flight mass spectrometer for diluted samples has been available for users at the FinEstBeAMS beamline of the MAX IV Laboratory in Lund, Sweden. The setup enables users to study the interaction of atoms, molecules, (molecular) microclusters and nanoparticles with short-wavelength (vacuum ultraviolet and X-ray) synchrotron radiation and to follow the electron and nuclear dynamics induced by this interaction. Test measurements of N2 and thiophene (C4H4S) molecules have demonstrated that the setup can be used for many-particle coincidence spectroscopy. The measurements of the Ar 3p photoelectron spectra by linear horizontal and vertical polarization show that angle-resolved experiments can also be performed. The possibility to compare the electron spectroscopic results of diluted samples with solid targets in the case of Co2O3 and Fe2O3 at the Co and Fe L2,3-absorption edges in the same experimental session is also demonstrated. Because the photon energy range of the FinEstBeAMS beamline extends from 4.4 eV up to 1000 eV, electron, ion and coincidence spectroscopy studies can be executed in a very broad photon energy range.

Fluorescence micro-spectroscopy study of individual photosynthetic membrane vesicles and light-harvesting complexes.

Single-molecule spectroscopy, by getting rid of unwanted ensemble averaging effects, has proved to be a very valuable tool in the research of individual photosynthetic light-harvesting (LH) complexes. However, to learn about real photosynthetic processes the minimal unit to study is a single photosynthetic membrane complete with all elements of its machinery. In the present work, the fluorescence spectra of excitons in lone intracytoplasmic (IC) photosynthetic membrane vesicles of the wild type purple bacterium Rhodobacter sphaeroides that involve peripheral (LH2) and core (RC-LH1-PufX) antenna pigment-protein complexes were investigated at ambient temperature under continuous-wave laser excitation into the Q(x) absorption band of the bacteriochlorophyll-a (BChl) chromophores at 594 nm. In parallel, the spectra of mutant membrane vesicles occupied by just one type of complexes (either LH2 or RC-LH1-PufX) and the spectra of individual purified LH2 and RC-LH1-PufX complexes were measured. The fluorescence from full IC membranes shows a high sensitivity to excitation intensity, being varied over more than four orders of magnitude between 0.1 W/cm(2) and 2 kW/cm(2). At low to moderate excitation intensities, the spectra of IC membranes could be well reproduced by its component spectra, the ratio of the spectra related to peripheral and core complexes being the only adjustable parameter. The spectra of both intact chromatophores and individual membrane components recorded over 1-50 s experimental time frames are robust, strongly suggesting that large spectral fluctuations hardly play a role in the functional photosynthetic process. The significant, up to 14 times, variation of the LH2 and LH1 emission ratio observed in individual IC membranes could be related to variations in the stoichiometric ratio of the peripheral and core complexes. Evidence was found for the presence of LH2 parts that are detached from efficient energy transfer pathways. Upon strong and prolonged illumination, the membrane spectra reveal significant permanent modifications. These alterations, which mostly concern peripheral antenna complexes, were shown to be due to photo-oxidation of various numbers of BChl molecules in the B850 compartment of LH2.