Frequency Spectra of Quantum Beats in Nuclear Forward Scattering of 57Fe: The Mössbauer Spectroscopy with Superior Energy Resolution

Abstract

Frequency spectra of quantum beats (QB) in nuclear forward scattering (NFS) are analysed and compared to Mössbauer spectra. Lineshape, number of lines, sensitivity to minor sites, and other specific properties of the frequency spectra are discussed. The most characteristic case of combined magnetic and quadrupole interactions is considered in detail for 57 Fe. Pure magnetic Zeeman splitting corresponds to a eight-line spectrum of QB, six of which show the same energy separation as the six lines in Mössbauer spectra. Two other lines (called 2 and 3 ) are the lower-energy satellites of the lines 2 and 3. As the quadrupole interaction E Q appears, the satellites remain unsplit in the quantum beat frequency spectra, as well as the first (zero-frequency) and the 6th (largest frequency) lines. Each of the lines 3 and 5 generates a doublet split by 2E Q , and the lines 2 and 4 generate triplets. In QB frequency spectra (QBFS) of thin absorbers of GdFeO 3 we demonstrate the enhanced spectral resolution compared to Mössbauer spectra. Small particle size in an antiferromagnet (Fe 2 O 3 ) was found to affect the QBFS via enhancement of the intensity around zero-frequencies. An asymmetric hyperfine field distribution mixes up into the hybridization with dynamical beats, which enlarges the frequencies of the low-lying QBFS lines and makes their shifts relatively large compared to the shift of the highest-frequency line.

Nuclear forward scattering in particulate matter: dependence of lineshape on particle size distribution

“…The magnetic hyperfine field of 500 kOe and zero quadrupole splitting are assumed. Very close hyperfine parameters were observed previously in GdFeO 3 [11]. Spectral weight of the quantum beat frequency spectra shown in Fig.…”

An Ising ferrimagnet with layered and chained magnetic sublattices:

“…5 we find no strong high-frequency QB. The suppression of the QB with increasing frequency may originate from broadening the QBFS spectral lines due to thickness effects [16]. Such a progressive broadening is shown schematically in theoretical QBSF spectra.…”

“…Such a long time window is suitable to suppress the effects of a finite time window in the quantum beats frequency spectra (QBFS) [16]. The current between 60 and 30 mA and the beam lifetime of 1200 min have allowed accumulating the high quality spectra within ' 3 h per sample.…”

“…The oxide Ca 2 FeMnO 5 was characterized by the methods of nuclear forward scattering [16] and nuclear inelastic scattering [2]. Fig.…”

The Prime Beat Components Extraction Method for the Time Spectra Analysis of Nuclear Resonant Forward Scattering

“…To the best of our knowledge, there is still no relevant research work on interpreting the origins of these spectral lines. Different from the method of transforming QBs to a frequency spectrum with an adaptable window [19], the treatment of data is to convert the QBs to its frequency space by the maximum entropy method (MEM) [20]. This frequency information is explained by a method named “prime beat components (PBCs) extraction method”, which is inspired by the spectrum analysis of time series in signal processing [21] and based on the principle that the NFS is a coherent process.…”