Nuclear Resonance Vibrational Spectroscopy on:
[Wikipedia]
[Google]
[Amazon]
Nuclear resonance vibrational spectroscopy is a
In the experimental setup, X-rays are released from the particle beam by an undulator; a high-resolution monochromator produces a beam with small energy dispersion (typically 1.0 meV). The sample is irradiated with photons chosen around the resonance of the Mössbauer isotope and further information is provided for the specific isotope. Typical parameters for the experimental scan are –20 meV below recoil-free resonance energy to +100 meV above it. The number of scans (often recorded for 5 seconds every 0.2 meV) depends on the amount of Mössbauer-active nuclei in the sample. The number of photons absorbed by the sample at any wavelength are measured by detecting the fluorescence emitted from the excited atom with an avalanche photodiode detector. The resulting raw spectrum contains a high-intensity resonance that corresponds to the nuclear excited state of the probed nucleus. For bulk samples, the technique detects natural abundance 57Fe. For many dilute or biological samples, the sample is often enriched in 57Fe.
synchrotron
A synchrotron is a particular type of cyclic particle accelerator, descended from the cyclotron, in which the accelerating particle beam travels around a fixed closed-loop path. The magnetic field which bends the particle beam into its closed p ...
-based technique that probes vibrational energy levels. The technique, often called NRVS, is specific for samples that contain nuclei that respond to Mössbauer spectroscopy
Mössbauer spectroscopy is a spectroscopic technique based on the Mössbauer effect. This effect, discovered by Rudolf Mössbauer (sometimes written "Moessbauer", German: "Mößbauer") in 1958, consists of the nearly recoil-free emission and abso ...
, most commonly iron. The method exploits the high resolution offered by synchrotron light sources, which enables the resolution of vibrational fine structure, especially those vibrations that are coupled to the position of the Fe centre(s). The method is popularly applied to problems in bioinorganic chemistry
Bioinorganic chemistry is a field that examines the role of metals in biology. Bioinorganic chemistry includes the study of both natural phenomena such as the behavior of metalloproteins as well as artificially introduced metals, including those t ...
, materials science, and geophysics
Geophysics () is a subject of natural science concerned with the physical processes and physical properties of the Earth and its surrounding space environment, and the use of quantitative methods for their analysis. The term ''geophysics'' som ...
. A novel aspect of the method is the ability to determine the 3D-trajectory of iron atoms within vibrational modes, providing a unique appraisal of DFT-prediction accuracy.J. W. Pavlik, A. Barabanschikov, A. G. Oliver, E. E. Alp, W. Sturhahn, J. Zhao, J. T. Sage, W. R. Scheidt, "Probing Vibrational Anisotropy with Nuclear Resonance Vibrational Spectroscopy" , Angew. Chem. Int. Ed. 2010, volume 49, pp. 4400-4404. Other names for this method include nuclear inelastic scattering (NIS), nuclear inelastic absorption (NIA), nuclear resonant inelastic x-ray scattering (NRIXS), and phonon assisted Mössbauer effect.
Experimental set-up
In the experimental setup, X-rays are released from the particle beam by an undulator; a high-resolution monochromator produces a beam with small energy dispersion (typically 1.0 meV). The sample is irradiated with photons chosen around the resonance of the Mössbauer isotope and further information is provided for the specific isotope. Typical parameters for the experimental scan are –20 meV below recoil-free resonance energy to +100 meV above it. The number of scans (often recorded for 5 seconds every 0.2 meV) depends on the amount of Mössbauer-active nuclei in the sample. The number of photons absorbed by the sample at any wavelength are measured by detecting the fluorescence emitted from the excited atom with an avalanche photodiode detector. The resulting raw spectrum contains a high-intensity resonance that corresponds to the nuclear excited state of the probed nucleus. For bulk samples, the technique detects natural abundance 57Fe. For many dilute or biological samples, the sample is often enriched in 57Fe.
References
{{BranchesofSpectroscopy Vibrational spectroscopy Scientific techniques