THz-Beamline

Coherent & Incoherent THz Synchrotron Radiation

The THz beamline exploits intense coherent synchrotron radiation (CSR, [1-2]) as emitted from special storage ring modes, for the study of magneto optical phenomena in the energy range from 3 to 150 1/cm. A dedicated THz electron paramagnetic resonance (THz-EPR) facility combines a broad range of excitation and detection schemes with extreme sample environments (in particular high magnetic fields and low temperatures).

Science drivers for the THz beamline

Optical layout and schematic of the instrumental set-up at the THz beamline. THz radiation extracted from the storage ring may be readily directed towards three different detection schemes.

Research topics are related to manipulation and detection of high spin states in e.g., proteins, single molecule magnets, energy materials and materials relevant for future information technologies.

The THz beamline extracts CSR from the 2° dipole source (D112) after the slicing section at an acceptance of 60 mrad (h) x 15 mrad (v). A true optical transmission line transports CSR as emitted by ultra-short bunches in the low a mode (pulse length: < 10 ps, spectral range: 3-50 cm^-1)[1] and laser-induced by Femtoslicing [2] ( pulse length: ~ 200 fs, spectral range: 20-150 cm^-1), respectively. Complementary, FIR-UV-VIS cw radiation and 1 mJ of synchronized fs laser pulses (800 or 400 nm) are available at the experiment.  Sample environments include a superconducting magnet (Cryogenic Ltd., -12 T to +12 T) equipped with a variable temperature insert (1.8 K-400 K), and an optical cryostat (Oxford Optistat, T = 1.5 K- 300 K). THz detection is achieved either with a high resolution FTIR-spectrometer (Bruker IFS 125-HR, min. bandwidth: 0.0063 cm^-1) in combination with ultra-sensitive liquid helium cooled Si- or InSb – bolometers or fast Schottky diode THz detectors (ACST, time resolution 250 ps).  Alternatively, transient THz signals may be directly detected via a time domain (TD) THz set-up. This dedicated TD THz scheme allows for a cross-correlation of THz pulses from the storage ring with the synchronized external fs-laser source (optical pump – THz probe).

References / Selected Publications

[1] M. Abo-Bakr, J. Feikes, K. Holldack, P. Kuske, W. B. Peatman, U. Schade, G. Wustefeld and H. W. Hubers
Brilliant, coherent far-infrared (THz) synchrotron radiation
Phys. Rev. Lett. 90 (9), 094801 (2003)

[2] K. Holldack, S. Khan, R. Mitzner and T. Quast
Femtosecond terahertz radiation from femtoslicing at BESSY
Phys. Rev. Lett. 96 (5), 054801 (2006)

 [3] A. Schnegg, J. Behrends, K. Lips, R. Bittl and K. Holldack
Frequency domain Fourier transform THz-EPR on single molecule magnets using coherent synchrotron radiation
Phys. Chem. Chem. Phys. 11 (31), 6820-6825 (2009)

 [4] J. Nehrkorn, J. Telser, K. Holldack, S. Stoll and A. Schnegg
Simulating Frequency-Domain Electron Paramagnetic Resonance: Bridging the Gap between Experiment and Magnetic Parameters for High-Spin Transition-Metal Ion Complexes
J. Phys. Chem. B 119 (43), 13816-13824 (2015)

 [5] J. Nehrkorn, A. Schnegg, K. Holldack and S. Stoll
General magnetic transition dipole moments for electron paramagnetic resonance
Phys. Rev. Lett. 114 (1), 010801 (2015)

[6] J. Nehrkorn, K. Holldack, R. Bittl and A. Schnegg
Recent progress in synchrotron-based frequency-domain Fourier-transform THz-EPR
J. Magn. Reson. 280, 10-19 (2017)

[7] M. Rams, A. Jochim, M. Bohme, T. Lohmiller, M. Ceglarska, M. M. Rams, A. Schnegg, W. Plass and C. Nather
Single-Chain Magnet Based on Cobalt(II) Thiocyanate as XXZ Spin Chain
Chem. Eur. J. 26 (13), 2765 (2020)

[8] M. Tarrago, C. Romelt, J. Nehrkorn, A. Schnegg, F. Neese, E. Bill and S. Ye
Experimental and Theoretical Evidence for an Unusual Almost Triply Degenerate Electronic Ground State of Ferrous Tetraphenylporphyrin
Inorg. Chem. 60 (7), 4966-4985 (2021)

 [9] J. C. Ott, E. A. Suturina, I. Kuprov, J. Nehrkorn, A. Schnegg, M. Enders and L. H. Gade
Observability of Paramagnetic NMR Signals at over 10 000 ppm Chemical Shifts
Angew. Chem. Int. Ed. 60 (42), 22856-22864 (2021)

[10] T. Lohmiller, C. J. Spyra, S. Dechert, S. Demeshko, E. Bill, A. Schnegg and F. Meyer
Antisymmetric Spin Exchange in a mu-1,2-Peroxodicopper(II) Complex with an Orthogonal Cu-O-O-Cu Arrangement and S = 1 Spin Ground State Characterized by THz-EPR
JACS Au 2 (5), 1134-1143 (2022)

[11] T. Al Said, D. Spinnato, K. Holldack, F. Neese, J. Cornella and A. Schnegg
Direct Determination of a Giant Zero-Field Splitting of 5422 cm⁻¹ in a Triplet Organobismuthinidene by Infrared Electron Paramagnetic Resonance
J. Am. Chem. Soc. 147 (1), 84-87 (2025)

 [12] M. C. Neben, N. Wegerich, T. A. Al Said, R. R. Thompson, S. Demeshko, K. Dollberg, I. Tkach, G. P. Van Trieste, 3rd, H. Verplancke, C. von Hanisch, M. C. Holthausen, D. C. Powers, A. Schnegg and S. Schneider
Transient Triplet Metallopnictinidenes M-Pn (M = Pd(II), Pt(II); Pn = P, As, Sb): Characterization and Dimerization
J. Am. Chem. Soc. 147 (6), 5330-5339 (2025)

 [13] W. Chen, N. Kochetov, T. Lohmiller, Q. Liu, L. Deng, A. Schnegg and S. Ye
A Spectroscopic Criterion for Identifying the Degree of Ground-Level Near-Degeneracy Derived from Effective Hamiltonian Analyses of Three-Coordinate Iron Complexes
JACS Au 5 (2), 1016-1030 (2025)