Mossbauer spectra

7/29/2019 Mossbauer spectra

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Mssbauer spectroscopy

A Mssbauer absorption spectrum of57Fe

Mssbauer spectroscopy is a spectroscopictechnique based on the Mssbauer effect. Thiseffect, discovered by Rudolf Mssbauerin 1957, consists of the recoil-free, resonant absorption

and emission ofgamma raysin solids.

LikeNMR spectroscopy, Mssbauer spectroscopy probes tiny changes in the energy levels of an

atomic nucleus in response to its environment. Typically, three types ofnuclear interaction maybe observed: an isomer shift, also known as achemical shift;quadrupole splitting; and magnetic

orhyperfine splitting, also known as the Zeeman effect. Due to the high energy and extremely

narrow line widths of gamma rays, Mssbauer spectroscopy is a very sensitive technique interms of energy (and hence frequency) resolution, capable of detecting change in just a few parts

per 1011.

Basic principle

Just as a gun recoils when a bullet is fired, conservation of momentum requires a free nucleus(such as in a gas) to recoil during emission or absorption of a gamma ray. If a nucleus at rest

emits a gamma ray, the energy of the gamma ray is slightly less than the natural energy of the

transition, but in order for a nucleus at rest to absorb a gamma ray, the gamma ray's energy mustbe slightly greater than the natural energy, because in both cases energy is lost to recoil. This

means that nuclear resonance (emission and absorption of the same gamma ray) is unobservable

with free nuclei, because the shift in energy is too great and the emission and absorption spectra

have no significant overlap.

Nuclei in a solid crystal, however, are not free to recoil because they are bound in place in the

crystal lattice. When a nucleus in a solid emits or absorbs a gamma ray, some energy can still be

lost as recoil energy, but in this case it always occurs in discrete packets called phonons

(quantized vibrations of the crystal lattice). Any whole number of phonons can be emitted,including zero, which is known as a "recoil-free" event. In this case conservation of momentum

is satisfied by the momentum of the crystal as a whole, so practically no energy is lost.
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As an analogy, imagine jumping from a boat to shore, and imagine that the distance from the

boat to shore is the longest you can possibly jump (on land). If the boat is floating in water, you

will fall short because some of your energy goes into pushing the boat back. If the water isfrozen solid, however, you will be able to make it.

Mssbauer found that a significant fraction of emission and absorption events will be recoil-free,which is quantified using the LambMssbauer factor.[2] This fact is what makes Mssbauer

spectroscopy possible, because it means gamma rays emitted by one nucleus can be resonantlyabsorbed by a sample containing nuclei of the same isotope, and this absorption can be

measured.

Typical method

In its most common form, Mssbauer absorption spectroscopy, a solid sample is exposed to abeam ofgamma radiation, and a detector measures the intensity of the beam transmitted through

the sample. The atoms in the source emitting the gamma rays must be of the same isotope as the

atoms in the sample absorbing them.

If the emitting and absorbing nuclei were in identical chemical environments, the nucleartransition energies would be exactly equal and resonant absorption would be observed with both

materials at rest. The difference in chemical environments, however, causes the nuclear energy

levels to shift in a few different ways, as described below. Although these energy shifts are tiny(often less than a micro-electronvolt), the extremely narrow spectral linewidthsof gamma rays

for some radionuclides make the small energy shifts correspond to large changes in absorbance.

To bring the two nuclei back into resonance it is necessary to change the energy of the gammaray slightly, and in practice this is always done using theDoppler effect.

During Mssbauer absorption spectroscopy, the source is accelerated through a range ofvelocities using a linear motor to produce a Doppler effect and scan the gamma ray energy

through a given range. A typical range of velocities for57Fe, for example, may be 11 mm/s(1 mm/s = 48.075 neV).

In the resulting spectra, gamma ray intensity is plotted as a function of the source velocity. At

velocities corresponding to the resonant energy levels of the sample, a fraction of the gamma

rays are absorbed, resulting in a drop in the measured intensity and a corresponding dip in thespectrum. The number, positions, and intensities of the dips (also called peaks; dips in

transmitted intensity are peaks in absorbance) provide information about the chemical

environment of the absorbing nuclei and can be used to characterize the sample.

Selecting a suitable source

Mssbauer spectroscopy is limited by the need for a suitable gamma-ray source. Usually, thisconsists of a radioactive parent that decays to the desired isotope. For example, the source for57Fe consists of57Co, which decays by electron capture to anexcited state of57Fe, then

subsequently decays to a ground state emitting the desired gamma-ray. The radioactive cobalt isprepared on a foil, often of rhodium.[4] Ideally theparent isotope will have a sufficiently long
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half-life to remain useful, but will also have a sufficient decay rate to supply the required

intensity of radiation. Also, the gamma-ray energy should be relatively low, otherwise the system

will have a low recoil-free fraction resulting in a poorsignal-to-noise ratio and requiring longcollection times. The periodic table below indicates those elements having an isotope suitable for

Mssbauer spectroscopy. Of these,57Fe is by far the most common element studied using the

technique, although129

I,119

Sn, and121

Sb are also frequently studied.

[hide]

Periodic table of Mssbauer active elements

H He

Li Be B C N O F Ne

Na Mg Al Si P S Cl Ar

K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr

Rb Sr Y ZrNb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe

Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn

Fr Ra Ac Rf Db Sg Bh Hs Mt Ds Rg Cn Uut Fl Uup Lv Uus Uuo

Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr

Mssbauer-active elements Gamma-ray sources Unsuitable for Mssbauer

Analysis of Mssbauer spectra

As described above, Mssbauer spectroscopy has an extremely fine energy resolution and candetect even subtle changes in the nuclear environment of the relevant atoms. Typically, there are

three types ofnuclear interactions that are observed, isomer shift (orchemical shift), quadrupole

splitting and hyperfine splitting (orZeeman splitting).[5][6]

Isomer shift () is a relative measure describing a shift in the resonance energy of a nucleus due

to the transition of electrons within itss orbital. The whole spectrum is shifted in either a positive

or negative direction depending upon the s electron charge density. This change arises due to

alterations in the electrostatic response between the non-zero probability s orbital electrons andthe non-zero volume nucleus they orbit.

Only electrons in s orbitals demonstrate non-zero probability because their 3D spherical shape

incorporates the volume taken up by the nucleus. However, the p, d, and other electrons may

influence the s electron density through a screening effect. The s electron density can also beaffected by the oxidation state and the chemical environment of the atom.

Isomer shift (chemical shift, CS) can be expressed using the formula below, where K is a nuclear

constant, the difference between Re2 and Rg

2 is the effective nuclear charge radius differencebetween excited state and the ground state, and the difference between [s

2(0)]a and [s2(0)]b is

the electron density difference on the nucleus (a = source, b = sample). Isomer shift does not
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.wikipedia.org/wiki/Curiumhttp://en.wikipedia.org/wiki/Berkeliumhttp://en.wikipedia.org/wiki/Californiumhttp://en.wikipedia.org/wiki/Einsteiniumhttp://en.wikipedia.org/wiki/Fermiumhttp://en.wikipedia.org/wiki/Mendeleviumhttp://en.wikipedia.org/wiki/Nobeliumhttp://en.wikipedia.org/wiki/Lawrenciumhttp://en.wikipedia.org/wiki/Nuclear_interactionhttp://en.wikipedia.org/wiki/Chemical_shifthttp://en.wikipedia.org/wiki/Quadrupole_splittinghttp://en.wikipedia.org/wiki/Quadrupole_splittinghttp://en.wikipedia.org/wiki/Hyperfine_splittinghttp://en.wikipedia.org/wiki/Zeeman_splittinghttp://en.wikipedia.org/wiki/M%C3%B6ssbauer_spectroscopy#cite_note-RSC2-5http://en.wikipedia.org/wiki/M%C3%B6ssbauer_spectroscopy#cite_note-G.C3.BCtlich_et_al-6http://en.wikipedia.org/wiki/Screening_effecthttp://en.wikipedia.org/wiki/Isomer_shifthttp://en.wikipedia.org/wiki/Chemical_shift


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change with temperature, however, a small changes are generally attributed to second-order

Doppler effect.

CS = K (Re2 Rg

2) {[s2(0)]a [s

2(0)]b}

Chemical shift and quadrupole splitting of the nuclear energy levels and correspondingMssbauer spectra

The physical meaning of this equation can be clarified using examples:

1. While an increase ins electron density in 57Fe spectrum gives a negative shift because the

change in the effective nuclear charge is negative, an increase in s electron density in119Sn gives a positive shift due to a positive change in overall nuclear charge.

2. Oxidised ferric ions (Fe3+) have lower isomer shifts than ferrous ions (Fe2+) because s

electron density at the nucleus of ferric ions is greater due to a weaker screening effect by

delectrons.[7]

Quadrupole Splitting reflects the interaction between the nuclear energy levels and surrounding

electric field gradient (EFG). Nuclei in states with non-spherical charge distributions, i.e. all

those with angular quantum number (I) greater than 1/2, produce an asymmetrical electric field

which splits the nuclear energy levels. This produces a nuclear quadrupole moment.[5]

In the case of an isotope with a I=3/2 excited state, such as 57Fe or119Sn, the 3/2 to 1/2 transition

is split into two substates mI=1/2 and mI=3/2. These appear as two specific peaks in a

spectrum, sometimes referred to as a 'doublet'. Quadrupole splitting is measured as the separationbetween these two peaks and reflects the character of the electric field at the nucleus.
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Magnetic splitting of the nuclear energy levels and the corresponding Mssbauer spectrum

Magnetic splitting (hyperfine splitting) is a result of the interaction between the nucleus any

surrounding magnetic field. A nucleus with spin, I, splits into 2I + 1 sub-energy levels in thepresence of magnetic field. For example, a nucleus with spin state I= 3/2 will split into 4 non-

degenerate sub-states with mI values of +3/2, +1/2, -1/2 and 3/2. Each split is hyperfine, being

in the order of 107eV. The restriction rule of magnetic dipoles means that transitions between

the excited state and ground state can only occur where m I changes by 0 or 1. This gives sixpossible transitions for a 3/2 to 1/2 transition.[5] Generally speaking therefore, in the majority of

cases only six peaks can be monitored in a spectrum produced by a hyperfine splitting nucleus.

The three Mssbauer parameters: isomer shift, quadrupole splitting, and hyperfine splitting can

often be used to identify a particular compound by comparing it to known spectra. A largedatabase including most of the published Mssbauer parameters available in the literature is

maintained by the Mssbauer Effect Data Center.[8]In some cases, a compound may have more

than one possible position for the Mssbauer active atom. For example, the crystal structure ofmagnetite (Fe3O4) supports two unique sites for the iron atoms. The corresponding spectrum

therefore has twelve peaks, a 'hextet' for each potential atomic site. Thus, magnetite also has two

sets of Mssbauer parameters, one for each site.

Combination of all: Many times it is very common to observe all effects-isomer shift,

quadrupole splitting and magnetic Zeeman effect- in a spectrum. In such cases the isomer shift is

given by the average of all lines. The quadrupole splitting when all the four excited substates are

equally shifted (two substates are lifted and other two are lowered) is given the shift of the outertwo lines relative to the inner two lines (generally innermost two lines are not considered). If the

shifting of four substates are not equal then the quadrupole splitting is often extracted using

fitting software where all the six lines are taken in to account.

In addition, the relative intensities of the various peaks reflect the relative concentrations ofcompounds in a sample and can be used for semi-quantitative analysis. Also, since ferromagnetic
http://en.wikipedia.org/wiki/Hyperfine_splittinghttp://en.wikipedia.org/wiki/M%C3%B6ssbauer_spectroscopy#cite_note-RSC2-5http://en.wikipedia.org/w/index.php?title=M%C3%B6ssbauer_Effect_Data_Center&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=M%C3%B6ssbauer_Effect_Data_Center&action=edit&redlink=1http://en.wikipedia.org/wiki/M%C3%B6ssbauer_spectroscopy#cite_note-8http://en.wikipedia.org/wiki/M%C3%B6ssbauer_spectroscopy#cite_note-8http://en.wikipedia.org/wiki/Magnetitehttp://en.wikipedia.org/wiki/Magnetitehttp://en.wikipedia.org/wiki/File:Mossbauer_-Magnetting_Splitting.jpghttp://en.wikipedia.org/wiki/File:Mossbauer_-Magnetting_Splitting.jpghttp://en.wikipedia.org/wiki/Hyperfine_splittinghttp://en.wikipedia.org/wiki/M%C3%B6ssbauer_spectroscopy#cite_note-RSC2-5http://en.wikipedia.org/w/index.php?title=M%C3%B6ssbauer_Effect_Data_Center&action=edit&redlink=1http://en.wikipedia.org/wiki/M%C3%B6ssbauer_spectroscopy#cite_note-8http://en.wikipedia.org/wiki/Magnetite


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phenomena are size-dependent, in some cases spectra can provide insight into the crystallite size

and grain structure of a material.

Applications of Mssbauer spectroscopy

Among the drawbacks of the technique are the limited number of gamma ray sources and therequirement that samples be solid in order to eliminate the recoil of the nucleus. Mssbauer

spectroscopy is unique in its sensitivity to subtle changes in the chemical environment of the

nucleus including oxidation state changes, the effect of different ligands on a particular atom,and the magnetic environment of the sample.

As an analytical tool Mssbauer spectroscopy offers detection limits in the order of billionths of

an electron volt.It has been especially useful in the field of geology for identifying the

composition of iron-containing specimens including meteors and moon rocks. In situ datacollection of Mssbauer spectra has also been carried out on iron rich rocks on Mars.[9]

Another significant application of Mssbauer spectroscopy is the study of phase transformationsthat occur in iron catalysts during FischerTropsch synthesis. While these catalysts initially

consist of hematite (Fe2O3), during reaction they are transformed into a mixture of magnetite(Fe3O4) and several iron carbides. The formation of carbides appears to improve catalytic

activity, however it can also lead to the mechanical break-up and attrition of the catalyst

particles. This can cause difficulties in the final separation of catalyst from reaction products.[10]

Mssbauer spectroscopy has also been used to determine the relative concentration change in theoxidation state of antimony (Sb) during the selective oxidation ofolefins. During calcinationall

the Sb ions in an antimony-containing tin dioxide catalyst transform into the +5 oxidation state.

Following the catalytic reaction, almost all Sb ions revert from the +5 to the +3 oxidation state.

A significant change in the chemical environment surrounding the antimony nucleus occursduring the oxidation state change which can easily be monitored as an isomer shift in the

Mssbauer spectrum.[11]

This technique has also been used to observe the second-ordertransverse Doppler effectpredicted by the theory of relativity, because of very high energy resolution. More recently,

Mssbauer spectroscopy has been instrumental in developing an understanding of the structure

and function of iron containing enzymes and the model complexes synthesized to mimic thefunctions of these enzymes. Some examples of enzymes characterized in this way are:

ribonucleotide reductasemethane monooxygenase,tryptophan dioxygenase,[17]deoxypusine

hydroxylase,[18]protocatechuate 2,3 dioxygenase, andcytochrome ba3

Mossbauer spectroscopy has also been used very successfully to investigate the electronicstructure ofheterobimetallic complexes.[21][22][23][24]

Mssbauer spectrometers
http://en.wikipedia.org/wiki/Ligandhttp://en.wikipedia.org/wiki/M%C3%B6ssbauer_spectroscopy#cite_note-9http://en.wikipedia.org/wiki/Fischer%E2%80%93Tropsch_synthesishttp://en.wikipedia.org/wiki/Magnetitehttp://en.wikipedia.org/wiki/Cementitehttp://en.wikipedia.org/wiki/M%C3%B6ssbauer_spectroscopy#cite_note-10http://en.wikipedia.org/wiki/M%C3%B6ssbauer_spectroscopy#cite_note-10http://en.wikipedia.org/wiki/Antimonyhttp://en.wikipedia.org/wiki/Olefinshttp://en.wikipedia.org/wiki/Calcinationhttp://en.wikipedia.org/wiki/Calcinationhttp://en.wikipedia.org/wiki/Tin_dioxidehttp://en.wikipedia.org/wiki/M%C3%B6ssbauer_spectroscopy#cite_note-11http://en.wikipedia.org/wiki/Transverse_Doppler_effecthttp://en.wikipedia.org/wiki/Theory_of_relativityhttp://en.wikipedia.org/wiki/Theory_of_relativityhttp://en.wikipedia.org/wiki/Methane_monooxygenasehttp://en.wikipedia.org/wiki/Methane_monooxygenasehttp://en.wikipedia.org/wiki/Methane_monooxygenasehttp://en.wikipedia.org/w/index.php?title=Tryptophan_dioxygenase&action=edit&redlink=1http://en.wikipedia.org/wiki/M%C3%B6ssbauer_spectroscopy#cite_note-17http://en.wikipedia.org/w/index.php?title=Deoxypusine_hydroxylase&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Deoxypusine_hydroxylase&action=edit&redlink=1http://en.wikipedia.org/wiki/M%C3%B6ssbauer_spectroscopy#cite_note-18http://en.wikipedia.org/wiki/M%C3%B6ssbauer_spectroscopy#cite_note-18http://en.wikipedia.org/w/index.php?title=Protocatechuate_2,3_dioxygenase&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Protocatechuate_2,3_dioxygenase&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Cytochrome_ba3&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Cytochrome_ba3&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Heterobimetallic_complex&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Heterobimetallic_complex&action=edit&redlink=1http://en.wikipedia.org/wiki/M%C3%B6ssbauer_spectroscopy#cite_note-21http://en.wikipedia.org/wiki/M%C3%B6ssbauer_spectroscopy#cite_note-22http://en.wikipedia.org/wiki/M%C3%B6ssbauer_spectroscopy#cite_note-23http://en.wikipedia.org/wiki/M%C3%B6ssbauer_spectroscopy#cite_note-24http://en.wikipedia.org/wiki/Ligandhttp://en.wikipedia.org/wiki/M%C3%B6ssbauer_spectroscopy#cite_note-9http://en.wikipedia.org/wiki/Fischer%E2%80%93Tropsch_synthesishttp://en.wikipedia.org/wiki/Magnetitehttp://en.wikipedia.org/wiki/Cementitehttp://en.wikipedia.org/wiki/M%C3%B6ssbauer_spectroscopy#cite_note-10http://en.wikipedia.org/wiki/Antimonyhttp://en.wikipedia.org/wiki/Olefinshttp://en.wikipedia.org/wiki/Calcinationhttp://en.wikipedia.org/wiki/Tin_dioxidehttp://en.wikipedia.org/wiki/M%C3%B6ssbauer_spectroscopy#cite_note-11http://en.wikipedia.org/wiki/Transverse_Doppler_effecthttp://en.wikipedia.org/wiki/Theory_of_relativityhttp://en.wikipedia.org/wiki/Methane_monooxygenasehttp://en.wikipedia.org/w/index.php?title=Tryptophan_dioxygenase&action=edit&redlink=1http://en.wikipedia.org/wiki/M%C3%B6ssbauer_spectroscopy#cite_note-17http://en.wikipedia.org/w/index.php?title=Deoxypusine_hydroxylase&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Deoxypusine_hydroxylase&action=edit&redlink=1http://en.wikipedia.org/wiki/M%C3%B6ssbauer_spectroscopy#cite_note-18http://en.wikipedia.org/w/index.php?title=Protocatechuate_2,3_dioxygenase&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Cytochrome_ba3&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Heterobimetallic_complex&action=edit&redlink=1http://en.wikipedia.org/wiki/M%C3%B6ssbauer_spectroscopy#cite_note-21http://en.wikipedia.org/wiki/M%C3%B6ssbauer_spectroscopy#cite_note-22http://en.wikipedia.org/wiki/M%C3%B6ssbauer_spectroscopy#cite_note-23http://en.wikipedia.org/wiki/M%C3%B6ssbauer_spectroscopy#cite_note-24


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A schematic view of mssbauer spectrometer

A Mssbauer spectrometer is a device that performs Mssbauer spectroscopy, or a device that

uses the Mssbauer effect to determine the chemical environment of Mssbauer nuclei present in

the sample. It is formed by three main parts; a source that moves back and forth to generate adoppler effect, a collimatorthat filters out non-parallel gamma raysand a detector.

A miniature Mssbauer Spectrometer, named (MB) MIMOS II, was used by the two rovers in

NASA'sMars Exploration Rovermissions.[25]

Notes on 57Fe Mssbauer spectroscopy

Sodium nitroprusside is a common reference material

The Mssbauer parameters: chemical isomer shift and quadrupole splitting are generally

evaluated with respect to a reference material. For example, in iron compounds, the Mssbauer

parameters were evaluated using iron foil (thickness less than 40 micrometers). The centroid ofthe six lines spectrum from metallic iron foil is 0.1 mm/s (forCo/Rh source). All shifts in other

iron compounds are computed relative to this 0.10 mm/s (at room temperature), i.e., in this case

isomer shifts are relative to Co/Rh source. In other words, the centre point of the Mssbauer

spectrum is zero. The shift values may also be reported relative to 0.0 mm/s, here shifts arerelative to the iron foil.

To calculate outer line distance from six line iron spectrum:
http://en.wikipedia.org/wiki/Doppler_effecthttp://en.wikipedia.org/wiki/Collimatorhttp://en.wikipedia.org/wiki/Gamma_rayshttp://en.wikipedia.org/wiki/Gamma_rayshttp://en.wikipedia.org/wiki/MIMOS_IIhttp://en.wikipedia.org/wiki/NASAhttp://en.wikipedia.org/wiki/NASAhttp://en.wikipedia.org/wiki/Mars_Exploration_Roverhttp://en.wikipedia.org/wiki/Mars_Exploration_Roverhttp://en.wikipedia.org/wiki/Mars_Exploration_Roverhttp://en.wikipedia.org/wiki/M%C3%B6ssbauer_spectroscopy#cite_note-25http://en.wikipedia.org/wiki/Cobalthttp://en.wikipedia.org/wiki/Cobalthttp://en.wikipedia.org/wiki/Rhodiumhttp://en.wikipedia.org/wiki/File:Sodium_nitroprusside_M%C3%B6ssbauer_spectrum.svghttp://en.wikipedia.org/wiki/File:Sodium_nitroprusside_M%C3%B6ssbauer_spectrum.svghttp://en.wikipedia.org/wiki/File:Mossbauer_Spectrometer.jpghttp://en.wikipedia.org/wiki/File:Mossbauer_Spectrometer.jpghttp://en.wikipedia.org/wiki/Doppler_effecthttp://en.wikipedia.org/wiki/Collimatorhttp://en.wikipedia.org/wiki/Gamma_rayshttp://en.wikipedia.org/wiki/MIMOS_IIhttp://en.wikipedia.org/wiki/NASAhttp://en.wikipedia.org/wiki/Mars_Exploration_Roverhttp://en.wikipedia.org/wiki/M%C3%B6ssbauer_spectroscopy#cite_note-25http://en.wikipedia.org/wiki/Cobalthttp://en.wikipedia.org/wiki/Rhodium


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where c is the velocity of light in m/s, Hint is the internal magnetic field of the metallic iron(33 T), N is the nuclear magneton (3.152451232610

8 eV/T), E is the excitation energy

(14.412497 keV),gn is the ground state nuclear splitting factor (0.09062/(I), whereIsospinI= 12)and g*

n is the excited state splitting factor of57Fe (0.1549/(I), whereI= 32).

By substituting the above values one would get V= 10.62 mm/s.

Other values are sometimes used to reflect different qualities of iron foils. In all cases any

change in Vonly affects the quadrupole splitting and not the isomer shift. As the IBAME, the

authority for Mssbauer spectroscopy, does not specify a particular value, anything between10.60 mm/s to 10.67 mm/s can be used.
http://en.wikipedia.org/wiki/M/shttp://en.wikipedia.org/wiki/Tesla_(unit)http://en.wikipedia.org/wiki/Nuclear_magnetonhttp://en.wikipedia.org/wiki/Nuclear_magnetonhttp://en.wikipedia.org/wiki/Electronvolthttp://en.wikipedia.org/wiki/Isospinhttp://en.wikipedia.org/wiki/Isospinhttp://en.wikipedia.org/w/index.php?title=International_Board_on_the_Applications_of_the_M%C3%B6ssbauer_Effect&action=edit&redlink=1http://en.wikipedia.org/wiki/M/shttp://en.wikipedia.org/wiki/Tesla_(unit)http://en.wikipedia.org/wiki/Nuclear_magnetonhttp://en.wikipedia.org/wiki/Electronvolthttp://en.wikipedia.org/wiki/Isospinhttp://en.wikipedia.org/w/index.php?title=International_Board_on_the_Applications_of_the_M%C3%B6ssbauer_Effect&action=edit&redlink=1

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Mossbauer spectra