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    Qiming Sun

    Nuclear resonant scattering is a synchrotron-based technique that probes hyperfine energy levels. The technique is specific for the electronic and magnetic structure of very small volumes like micro- and nano-structures and samples under extreme conditions of temperature and pressure.

    The process can be divided into three steps:

    1.A sync pulse of mono frequency excites the sample. Take the example of 57Fe, according to the uncertainty principle, the 14.4 keV excitation level in 57Fe is only few neV wide, which corresponds to the lifetime of 140 ns. If a 100 ps long pulse of synchrotron radiation hits a 57Fe sample, the subsequent fluorescence or the scattering occurs after a mean delay time of the order of 140 ns.

    2.The charge around the nucleus, the electric field gradient and the hyperfine magnetic field may change and split the nuclear level. Changes and splitting of energy levels can be used to detect the environment in which the core is embedded. In this way, valence, local symmetry, charge distribution, and magnetic moment can be determined locally around the probe core.

    3.In the case of hyperfine interactions, de-excitation amplitude disturbances cause oscillations (quantum beats) in the scattering intensity over time. The period and amplitude of these oscillations contain the above mentioned magnetic and electronic properties.

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