TGM Beamline

The TGM (Toroidal Grating Monochromator) beamline is dedicated to ultraviolet spectroscopy techniques in the energy range of 3 to 330 eV (ca. 400 to 4 nm). At this energy range, it is possible to perform studies related to the electronic structure and luminescence properties of solids, as well as on gas and solids subjected to conditions mimicking the atmospheric and astrophysical environments.

The TGM beamline was the first beamline to be built and made available for the users` community at the UVX storage ring of LNLS, and it has been in continuous operation since 1997. It is a spectroscopy beamline, based on a 1.67T bending magnet. It has a monochromator with three toroidal gratings and currently operates from 3 eV (413.28 nm) to 330 eV (3.75 nm), in ultra-high vacuum conditions. To ensure energy purity on the spectrum, it counts with a differentially-pumped gas filter (He, Ne, Ar, Kr), with different upper-energy cutoffs on the ionization threshold of the gases (24.6, 21.6, 15.7 and 14.1 eV, respectively), in addition to solid-state filters (glass, quartz and MgF2) for lowers energies (4.1, 8.2, 10.9 eV, respectively). Above 50 eV, the geometry of the beamline acts as an efficient cutoff of higher harmonics.

This beamline covers an important range of energy for studies of X-ray absorption of very light elements such as the K-edge of Li and the L-edge of environmentally significant ones (P, S, Cl, K). It is possible to directly assess the electronic structure of semi-conductors and insulators, to measure the luminescence of solids, photodegradation and photoionization of polymers and biomolecules, simulation of space and astrophysical conditions, and to do mass spectrometry.

Future planned experimental stations for this beamline include a Photoemission Microscope (PEEM), Circular Dichroism on the UV, for structural biology, and a dedicated chamber for optical measurements, including a setup for cryogenic studies.

## EXPERIMENTAL TECHNIQUES

The following experimental techniques and setups are available to users in this beamline. To learn more about the techniques’ limitations and requirements (sample, environment, etc.) contact the beamline coordinator before submitting your proposal.

###### PHOTOLUMINESCENCE (PL)

Photoluminescence (PL) in the vacuum ultraviolet energy range is used to investigate the region of the optical band gap and valence band in crystalline solids. Using the PL technique, it is possible to describe the valence band, the band gap length, the position of energy levels and understanding their role during the optical process. This information may allow the development of new and customized materials for specific applications, such as biomarkers, radiation detectors, lasers, light emitting diodes (LED), phosphors for illumination devices, energy-harvesting materials, etc.

Setup: The PL setup is composed by two main modes of detection. For the first one, the excitation mode, an optical fiber is positioned in angle with the sample and the fiber cable is coupled in a photomultiplier (PMT) for integrating the light emitted by the sample after the interaction with the synchrotron radiation. This signal gives information of the excitation of the sample in a specific range of energy. The second setup is the emission one. It is similar to the first and the difference is that the optical fiber is now coupled to a spectrometer (200 – 900 nm), allowing the retrieval of the profile of the emission spectra after excitation at specific energies. The flexible setup of the detection/control of the beamline allows different complementary setups: (i) monitor the emission intensity as a function of both emission and excitation energies; (ii) time-resolved studies (for persistent and fluorescent samples). Total Electron Yield (TEY) has also been used in these studies to monitor the behavior of the sample in absorption.

Recent publications using this setup:

1. Segreto, A.A. Machado, W. Araujo, V. Teixeira, “Delayed light emission of Tetraphenyl-butadiene excited by liquid argon scintillation light. Current status and future plans” Journal of Instrumentation, v. 11, n. 02, p. C02010, 2016. doi:10.1088/1748-0221/11/02/C02010
2. C. Teixeira, L.C.V. Rodrigues, D. Galante, M.V.S. Rezende, “Effect of lithium excess on the LiAl5O8:Eu luminescent properties under VUV excitation” Optical Materials Express, v. 6, n. 9, p. 2871-2878, 2016. doi: 10.1364/OME.6.002871
3. C.S. Pedroso, J.M. Carvalho, L.C.V. Rodrigues, J. Höslä, H.F. Brito, “Rapid and Energy Saving Microwave-Assisted Solid-State Synthesis of Pr3+, Eu3+ or Tb3+ Doped Lu2O3 Persistent Luminescence Materials” ACS Applied Materials & Interfaces, 2016. doi: 10.1021/acsami.6b04683
4. S. Bezerra, M.E.G. Valerio, “Structural and optical study of CaF2 nanoparticles produced by a microwave-assisted hydrothermal method”. Physica B: Condensed Matter, v. 501, p. 106-112, 2016. doi: 10.1016/j.physb.2016.08.025

###### SAMPLE IRRADIATION AND MASS SPECTROMETRY

The beamline can be used as a light source with unique characteristics. This mode is specially interesting to cover the wavelengths below 280 nm (UVB), deeper on the UV (down to 4nm), which is present, for instance, on space conditions. In addition to producing monochromatic light, the beamline can operate in white-beam mode (full spectrum) and pink-beam mode (white-beam with the low-pass gas filter, to introduce a cutoff on the higher energies). These modes can be used to simulate the Solar radiation in space to test materials for the aerospace industry (specially polymers), and also as sources of light for astrophysics, astrochemistry in gas and solid phases, and to probe the resistance of biomolecules and microorganisms under space or planetary simulations, for astrobiology.

Setup: in this mode, the beamline normally operates with a standard chamber for the irradiation of the material. If needed, different measurement systems can be mounted to monitor the sample in situ and in real time, such as mass spectrometers (QMS, ToF) or other spectroscopic techniques (UV-Vis and Raman). Customized setups can be arranged if feasible, with prior contact with the beamline staff.

Recent publications using this setup:

1. M. Betancourt, L.H. Coutinho, R. B. Bernini, C.E.V. Moura, A B. Rocha, G. G. B. Souza. “VUV and soft x-ray ionization of a plant volatile: Vanillin (C8H8O3). The Journal of chemical physics, v. 144, n. 11, p. 114305, 2016. doi:10.1063/1.4944084.
2. C. Abrevaya, I.G. Paulino-Lima, D. Galante, F. Rodrigues, P.J.D. Mauas, E. Cortón, C.A.S. Lage. “Comparative survival analysis of Deinococcus radiodurans and the Haloarchaea Natrialba magadii and Haloferax volcanii exposed to vacuum ultraviolet irradiation. Astrobiology, v. 11, n. 10, p. 1034-1040, 2011. doi:10.1089/ast.2011.0607.
3. S. Arruda, A. Medina, J.N. Sousa, L.A.V. Mendes, R.R.T. Marinho, F.V. Prudente, “Communication: Protonation process of formic acid from the ionization and fragmentation of dimers induced by synchrotron radiation in the valence region”. The Journal of chemical physics, v. 144, n. 14, p. 141101, 2016. doi: 10.1063/1.4945807

## LAYOUT & OPTICAL ELEMENTS

ElementTypePosition [m]Description
SOURCEBending Magnet-Bending Magnet D05 exit A (4°), 1.67T,
M1Toroidal focusing mirror-R = 93.23m
MonochromatorToroidal gratings, grazing incidence-Grating 1: 3 – 13 eV (Pt, 75 l/mm) Grating 2: 13 – 100 eV (Au, 200 l/mm) Grating 3: 100 – 330 eV (Au, 1800 l/mm)
M2Toroidal focusing mirror-R = 139.16m
M3Toroidal focusing mirror-R = 74.00m
Harmonics filtersGas and solids-Differentially pumped ​gas filter (up to 24.59 eV) Solid state filters: Glass, quartz and $\rm MgF_{2}$ windows

## PARAMETERS

ParameterValueCondition
Energy range [eV]3 - 330-
Energy resolution [$\Delta$E/E]500 -700effective
Beam size at sample [$\rm mm^{2}$, FWHM]1.02mm X 0.5mm
Flux density at sample [ph/s/$\rm mm^{2}$]$10^{9}$at 10 eV
Flux density at sample [ph/s/$\rm mm^{2}$]$5 \times 10 ^{11}$whitebeam
Polarization control-Entrance polarization slits (upper and lower)
to use natural polarization.

## INSTRUMENTATION

InstrumentTypeModelManufacturerSpecifications
DetectorPhotomultipliersR928 R316 R594-Hamamatsu
DetectorSilicon Photomultiplier (Si-PM)S13360-3025CS-Hamamatsu
DetectorEmission spectrographQE65000-Ocean optics
DetectorTotal electron Yield (TEY)6514 and 6485-Keithley
DetectorVUV ionization chamber---
Spectrometer Micro-Raman for off-line measurementsinViaExcitation lasers: 532, 633 and 785nm; Detector: CCD; Fast 2D and 3D mapping system; Fiber optics proves for in-process measurements; 5, 20, 50 and 100X objectives; Linkam temperature cell (-196°C – 600°C) Renishaw

## CONTROL AND DATA ACQUISITION

The beamline is controlled by EPICS, under Linux based systems, with most of the scripts in Python and a user-friendly graphic interface.

## HOW TO CITE THIS FACILITY

Users are required to acknowledge the use of LNLS facilities in any publications and to inform the Laboratory about any publications, thesis and other published materials. Users must also cooperate by supplying this information upon request.

Support text for acknowledgements:

This research used resources of the Brazilian Synchrotron Light Laboratory (LNLS), an open national facility operated by the Brazilian Centre for Research in Energy and Materials (CNPEM) for the Brazilian Ministry for Science, Technology and Innovations (MCTI). The _ _ _ beamline staff is acknowledged for the assistance during the experiments.

## OTHER REFERENCES

• L. Cavasso-Filho, M.G.P. Homem, R. Landers and A. N. Brito, “Advances on the Brazilian toroidal grating monochromator (TGM) beamline,” J. Electron. Spectrosc. Relat. Phenom. 144-147, 1125-1127 (2005).
• L. Cavasso-Filho, A.F. Lago, M.G.P. Homem, S. Pilling and A. N. Brito, “Delivering high-purity vacuum ultraviolet photons at the Brazilian toroidal grating monochromator (TGM) beamline,” J. Electron. Spectrosc. Relat. Phenom. 156-158, 168-171 (2007).

## PUBLICATIONS

Scientific publications produced with data obtained at the facilities of this beamline, and published in journals indexed by the Web of Science, are listed below.

Attention Users: Given the importance of the previous scientific results to the overall proposal evaluation process, users are strongly advised to check and update their publication record both at the SAU Online website and at the For the library, updates can be made by sending the full bibliographic data to the CNPEM library (biblioteca@cnpem.br). Publications are included in the database after being checked by the CNPEM librarians and the beamline coordinators.

Martins, F. H.; Paula, F. L. O.; Gomes, R. C.; Gomes, J. A.; Aquino, R.; Porcher, F.; Perzynski, R.; Depeyrot, J.. Local Structure Investigation of Core-Shell CoFe2O4@gamma-Fe2O3 Nanoparticles, Brazilian Journal of Physics, v.51, p. 47–59, 2021. DOI:10.1007/s13538-020-00829-9

Silva, L. F. da; Catto, A. C.; Bernardini, S.; Fiorido, T.; Palma, J. V. N. de ; Avansi Jr., W.; Aguir, K.; Bendahan, M.. BTEX gas sensor based on hematite microrhombuses, Sensors and Actuators B-Chemical, v. 326, p. 128817, 2020. DOI:10.1016/j.snb.2020.128817

Pereira, M. O.; Felix, V. de S. ; Oliveira-Carvalho, A. L.; Ferreira, D. S. R.; PImenta, A. R. ; Carvalho, C. S.; Silva, F. L. e; Pérez, C. A.; Galante, D.; Freitas, R. P. de. Investigating counterfeiting of an artwork by XRF, SEM-EDS, FTIR and synchrotron radiation induced MA-XRF at LNLS-BRAZIL, Spectrochimica Acta Part A-Molecular and Biomolecular Spectroscopy, v. 246, p. 118925, 2021. DOI:10.1016/j.saa.2020.118925

Lopes, N. A. ; Mertins, O.; Pinilla, C. M. B. ; Brandelli, A.. Nisin induces lamellar to cubic liquid-crystalline transition in pectin and polygalacturonic acid liposomes, Food Hydrocolloids, v. 112, p.106320, 2021. DOI:10.1016/j.foodhyd.2020.106320

Coura, R, L. C. ; Andrade, A. B.; Monteiro, T. de J.; Novais, S. M. V.; Macedo, Z. S.; Valerio, M. E. G.. Photoluminescent properties of BaF2 scintillator-polystyrene composite films under vacuum ultraviolet radiation, Materials Research Bulletin, v.135, p. 111159, 2021. DOI:10.1016/j.materresbull.2020.111159

Moreno, H.; Cortes, J. A. ; Praxedes, F. M. ; Freitas, S. M. de; Rezende, M. V. dos S.; Simões, A. Z. ; Teixeira, V. C.; Ramírez, M. A.. Tunable photoluminescence of CaCu3Ti4O12 based ceramics modified with tungsten, Journal of Alloys and Compounds, v.850, p. 156652, 2021. DOI:10.1016/j.jallcom.2020.156652

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