electron spin resonance sara lim & elizabeth ann pollock university of rochester phy 243:...
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![Page 1: Electron Spin Resonance Sara Lim & Elizabeth Ann Pollock University of Rochester PHY 243: Advanced Lab Professor Regina Demina](https://reader034.vdocuments.mx/reader034/viewer/2022051403/56649d4b5503460f94a282c9/html5/thumbnails/1.jpg)
Electron Spin Resonance
Sara Lim & Elizabeth Ann Pollock
University of Rochester
PHY 243: Advanced Lab
Professor Regina Demina
![Page 2: Electron Spin Resonance Sara Lim & Elizabeth Ann Pollock University of Rochester PHY 243: Advanced Lab Professor Regina Demina](https://reader034.vdocuments.mx/reader034/viewer/2022051403/56649d4b5503460f94a282c9/html5/thumbnails/2.jpg)
External Magnetic Field
Zeeman Effect Energy Splitting:
Landé Factor:
Apply an external magnetic field
For a Spin ½ system with a free electron (and zero angular momentum), g= 2
![Page 3: Electron Spin Resonance Sara Lim & Elizabeth Ann Pollock University of Rochester PHY 243: Advanced Lab Professor Regina Demina](https://reader034.vdocuments.mx/reader034/viewer/2022051403/56649d4b5503460f94a282c9/html5/thumbnails/3.jpg)
Spin in an External Magnetic FieldIn an external magnetic field, the spin is either parallel or anti-parallel to applied magnetic field
m = +1/2,-1/2
the energy levels: or
![Page 4: Electron Spin Resonance Sara Lim & Elizabeth Ann Pollock University of Rochester PHY 243: Advanced Lab Professor Regina Demina](https://reader034.vdocuments.mx/reader034/viewer/2022051403/56649d4b5503460f94a282c9/html5/thumbnails/4.jpg)
ResonanceAn electromagnetic field can induce magnetic dipole moment transitions if its frequency is near the energy difference:
When the levels have spacing ΔE||H the oscillatory magnetic field exerts a torque on the dipoles some of them reverse orientation, ie, they change energy levels: RESONANCE
Precessing
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Set-up
![Page 6: Electron Spin Resonance Sara Lim & Elizabeth Ann Pollock University of Rochester PHY 243: Advanced Lab Professor Regina Demina](https://reader034.vdocuments.mx/reader034/viewer/2022051403/56649d4b5503460f94a282c9/html5/thumbnails/6.jpg)
Set-up
![Page 7: Electron Spin Resonance Sara Lim & Elizabeth Ann Pollock University of Rochester PHY 243: Advanced Lab Professor Regina Demina](https://reader034.vdocuments.mx/reader034/viewer/2022051403/56649d4b5503460f94a282c9/html5/thumbnails/7.jpg)
Samples
![Page 8: Electron Spin Resonance Sara Lim & Elizabeth Ann Pollock University of Rochester PHY 243: Advanced Lab Professor Regina Demina](https://reader034.vdocuments.mx/reader034/viewer/2022051403/56649d4b5503460f94a282c9/html5/thumbnails/8.jpg)
Differences in samples
Valance electron acts analogously to H atom which has a free electron, so applying a magnetic field and sweeping allows observance of resonance
It is harder to observe resonance by sweeping magnetic field because ‘subshell’ of molecule is filled, so only a few electrons are free in copper sulfate complex. They are held closer to the complex, so they alternate spin up/down given the relaxation time. The inverse of the relaxation time- the time to reach equilibrium in spin states- is the width of the absorption peak.
![Page 9: Electron Spin Resonance Sara Lim & Elizabeth Ann Pollock University of Rochester PHY 243: Advanced Lab Professor Regina Demina](https://reader034.vdocuments.mx/reader034/viewer/2022051403/56649d4b5503460f94a282c9/html5/thumbnails/9.jpg)
DPPHCalculations (in cgs units)
Values obtained in lab (via gaussmeter and wavemeter)
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Errors/Uncertainty
Error in B-field- study with function generator- Imperfect B-field
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Problems- Oscilloscope dials- Do not apply more than 20 amps when sweeping the applied B field because the fuse will blow!