High-spin low-spin transition

Temperature dependent nuclear inelastic-scattering (NIS) of synchrotron radiation was applied to investigate both spin states of the spin-crossover complex [Fe(tpa)(NCS)(2)] (tpa = tris(2-pyridylmethyl)amine). A remarkable increase of the iron-ligand bond stretching upon spin crossover has unambiguously been identified by comparing the measured NIS spectra with theoretical simulations based on density-functional calculations

Single-nucleus quantum beats excited by synchrotron radiation

We have observed single-nucleus quantum beats in the incoherent scattering of synchrotron radiation by the 14.4 keV transition of $\rm {}^{57}Fe$. The 20 ns beat period characteristic of the nuclear excited-state splitting was clearly seen when enriched metallic samples were excited at the nuclear resonance energy or far from the resonance energy (i.e. accompanied by phonon excitation). The phase of the beat pattern is seen to change with the scattering angle in a manner consistent with the angular-momentum change of the (M1) transition

Single-nucleus quantum beats excited by synchrotron radiation

We have observed single-nucleus quantum beats in the incoherent scattering of synchrotron radiation by the 14.4 keV transition of 57Fe. The 20 ns beat period characteristic of the nuclear excited-state splitting was clearly seen when enriched metallic samples were excited at the nuclear resonance energy or far from the resonance energy (i.e. accompanied by phonon excitation). The phase of the beat pattern is seen to change with the scattering angle in a manner consistent with the angular-momentum change of the (M1) transition

Energy Dependence of Nuclear Recoil Measured with Incoherent Nuclear Scattering of Synchrotron Radiation

The energy dependences of nuclear forward scattering and nuclear 4π scattering of 14.4 keV synchrotron radiation were studied with an energy resolution of 6 meV. Nuclear 4π scattering resulted from internal conversion and therefore represents the energy dependence of resonant nuclear absorption. In the case of the [57Fe(bpp)2][BF4]2 sample the energy dependence of nuclear 4π scattering revealed a 13 meV inelastic broadening of the absorption line. This indicates an excitation of lattice motions in the nuclear absorption process. The technique allows the direct measurement of the energy distribution of nuclear recoil

The spin-crossover complex [ Fe(tpa)(NCS)

The temperature-induced spin crossover of iron(II) in the $[Fe(tpa)(NCS)_{2}]$ complex has been investigated by nuclear forward scattering (NFS), nuclear inelastic scattering (NIS), extended X-ray absorption fine structure (EXAFS) spectroscopy, conventional Mössbauer spectroscopy (MS) and by measurements of the magnetic susceptibility (SQUID). The various measurements consistently show that the transition is complete and abrupt and exhibits a hysteresis between 102 and 110 K. The dependence of the hyperfine parameters of the high-spin (HS) and of the low-spin (LS) phase on temperature is gradual while the effective thickness (determined by the Lamb-Mössbauer factor fLM) shows a step at the transition temperature. This step could be identified clearly because the effective thickness is measured directly by NFS. The Lamb-Mössbauer factor, the Debye temperature and the mean-square displacement of iron(II) could be determined for the HS and for the LS phase. When comparing the NIS data with the results from density functional theory (DFT), the Fe-N stretching vibrations of both LS and HS phases could be unambiguously identified and the fLM could be factorized for both phases into a lattice and a molecular part. The structural information from EXAFS and DFT geometry optimization are in reasonable agreement

Nuclear resonant scattering and molecular orbital calculations on an iron(II) spin‐crossover complex

Nuclear resonant scattering of synchrotron radiation was applied to investigate the spin‐crossover complex Fe(tpa)(NCS)2 (tpa=tris(2‐pyridylmethyl)amine). The nuclear forward scattering experiments are compared with conventional Mössbauer experiments, and the nuclear inelastic scattering experiments are compared with the results from a theoretical normal mode analysis based on molecular orbital calculations

Magnetism under high pressure studied by 57Fe\mathrm{^{57}Fe} and 151Eu\mathrm{^{151}Eu} nuclear scattering of synchrotron radiation

The nuclear forward scattering (NFS) of synchrotron radiation is especially suited for probing magnetism at very high pressure, here in the Mbar range, by the nuclear resonances of 57Fe and 151Eu. We report on high pressure (h.p.) NFS studies with the 14.4 keV transition of 57Fe on magnetic RFe2 Laves phases of cubic C15 structure (YFe2, GdFe2) and hexagonal C14 structure (ScFe2, TiFe2) at pressures up to 100 GPa (=1 Mbar). We present also h.p. NFS studies performed with the 21.5 keV resonance of 151Eu, probing the magnetism in the CsCl-type h.p. phase of EuTe