Outline for Presentation- Draft

      I.         Introduction/Background:

A.   Electron paramagnetic resonance (EPR) spectroscopy

1.     EPR is a technique for studying paramagnetic materials

a)     Paramagnetic materials are species that contain unpaired electrons

2.     Paramagnetic materials absorb microwave radiation when subjected to a magnetic field

3.     The frequency of microwave radiation generally used in EPR is in the range of 1-10 GHz

a)     Microwaves (300MHz-300GHz) represent a subset of electromagnetic radiation that are generally referred to as radio waves (3kHz-300GHz)

B.    Low frequency electron paramagnetic resonance (LFEPR) spectroscopy and EPR MOUSE

1.     LFEPR is a variation of EPR that utilizes a lower frequency radiation (around 300 MHz-1 GHz) than in conventional EPR which utilizes higher frequencies (1-10 GHz)

2.     EPR MOUSE is a further variation of EPR
3.  LFEPR, and EPR MOUSE devices have 2 main components
                a) The magnet which creates a magnetic field
                b) The radio frequency (RF) probe 
4. The equation, hν = gβB , represents the relationship between the applied magnetic field and the frequency of the absorbed radiation               
                     a) h = Planck’s constant, ν=frequency, g=g-factor    
            (constant), β= Bohr magneton (constant), B= 
             magnetic field

    II.         Rationale & Purpose:

A.   The goal of the first half of this project was to characterize the magnetic field of various magnet designs and measure the sensitivity of the RF probe to aid in the construction of the EPR MOUSE.

B.    The goal of the second half of this project is to demonstrate the capabilities of the current EPR MOUSE design and establish the feasibility of detecting paramagnetic species on a variety of surfaces of practical relevance.

C.    Advantages of LFEPR as opposed to EPR

1.     Can study larger objects non-invasively

a)     Conventional (higher frequency) EPR can only study samples smaller than 125mm³ in volume

b)    LFEPR can be used to study important cultural artifacts that are multiple liters in volume 

2.     Can study larger objects as opposed to EPR

D.   Advantages of EPR MOUSE

1.     Can study surfaces (the sample does not need to be placed inside a spectrometer)

a)     No sample size limitation

b)    Only limitation is the depth of penetration of the magnetic field and the radiation into the sample

  III.         Methods:

A.   Characterization of the magnetic field of different iron yoke designs

1.     Goal was to optimize the homogeneity of the magnetic field because the RF absorption is dependent on it.

2.     Used the Finite Element Method Magnetics (FEMM) software to generate the theoretical magnetic field distribution around the yoke

3.     Compared the theoretical prediction (using FEMM) to experimental measurements to ensure accuracy

B.    Determination of the sensitivity of the RF probe

1.     Used an EPR machine with a known homogenous magnetic field

2.     Measured using DPPH (2,2-diphenyl-1-picrylhydrazyl), a known paramagnetic species that is commonly used for EPR measurements

3.     Measured the sensitivity of the probe at numerous locations in the 3D space (in the XZ,YZ, and YX)

4.     Analyzed this data to determine the sensitivity of the RF probe

C.    Demonstration of the capabilities of the EPR MOUSE

1.     Currency

a)     Used the MOUSE to scan the surface of a US dollar bill and recorded the spatial distribution of the ferromagnetic signal, and created a 2D image.

2.     Paint/pigments

a)     Used the MOUSE to identify paramagnetic pigments used in various paints based off the signal produced

3.     Barcode

a)     Used the MOUSE to scan a barcode and record data based off its ferromagnetic signal (from toner ink) and created a 1D image of the barcode

 IV.         Results & Conclusion (not final)

A.   Based off the projects conducted to demonstrate the capabilities of the MOUSE, the EPR MOUSE has a number of potential applications including:

1.     Analysis of paintings and historical artifacts

2.     Authentication of currency and other paper documents

a)     Paramagnetic or ferromagnetic watermarks

3.     An alternative to optical barcode readers