Holders for Ultrafast Electron Spin Resonance Mary Lou P. Bailey - - PowerPoint PPT Presentation

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Holders for Ultrafast Electron Spin Resonance Mary Lou P. Bailey - - PowerPoint PPT Presentation

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Developing Sample Holders for Ultrafast Electron Spin Resonance Mary Lou P. Bailey EUREKA Intern Mentor: Devin T. Edwards Dr. Mark S. Sherwin UCSB Physics Department August 22, 2012 What is ESR Spectroscopy? Investigates unpaired

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SLIDE 1

Developing Sample Holders for Ultrafast Electron Spin Resonance

Mary Lou P. Bailey EUREKA Intern Mentor: Devin T. Edwards

  • Dr. Mark S. Sherwin

UCSB Physics Department August 22, 2012

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SLIDE 2
  • Investigates unpaired electron spins
  • Biology: Structures of protein complexes

ProteoRhodopsin Hexamer

What is ESR Spectroscopy?

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SLIDE 3

Electron Spin Resonance

  • Electrons spin-up or spin-down
  • Excitation causes precession

Spin-up and spin-down electrons B

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SLIDE 4

What Makes ESR at UCSB Unique?

  • Powered by Free Electron Laser (FEL)
  • Power 100,000x greater than a typical ESR experiment
  • Frequencies above 100 GHz
  • Strong Magnet
  • 12.5 Tesla = 200,000x magnetic field of the earth

Advantage: High power allows measurements of very rapid decaying spins

UCSB FEL

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SLIDE 5

Studying Biological Samples

Sample in here FEL pulse in ESR signal out (to detector)

Waveguide Sample Holder

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SLIDE 6

Sample Holders Reflect Pulse

Free Induction Decay (ESR signal)

  • Reflections interfere with

decaying spin signal

  • Must turn detector on 80 ns

after pulse shot

  • Goal: Reduce “dead-time”
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SLIDE 7

CAD 2D Sketches

Making New Sample Holders

Lathe Teflon and Rexolite rods

Machine Shop

Rod Drill Blade

Labels in inches x10

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SLIDE 8

Machined Sample Holders

Teflon Cylindrical Rexolite Cylindrical Teflon Cone Rexolite Cone Original Shape New Design

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SLIDE 9

Testing with the FEL

  • Raw data: Amp. v. time
  • Fourier Transform data to look at prominent frequencies
  • FEL frequency = 500 MHz (mixed down)

Amplitude Time (ns)

Before Fourier Transform

(Original Cylindrical Teflon)

FEL pulse Reflections from FEL pulse

0 20 40 60 80 100 (a. u.)

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SLIDE 10

Comparing FEL Pulse Reflections

0.00000 0.00066 0.00132 0.00198 0.00264

Amplitude (a. u.) Frequency (MHz)

Original Cylindrical Rexolite

  • Teflon reflects much more than Rexolite

0.00000 0.00066 0.00132 0.00198 0.00264

Amplitude

Amplitude (a. u.) Frequency (MHz)

Original Cylindrical Teflon

0 200 400 600 800 0 200 400 600 800

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SLIDE 11

Reflections from the Double Cone

0.00000 0.00066 0.00132 0.00198 0.00264

Amplitude (a. u.) Frequency (MHz)

Double Cone Teflon

0.00000 0.00066 0.00132 0.00198 0.00264

Amplitude

Amplitude (a. u.) Frequency (MHz)

Double Cone Rexolite

  • Two prominent peaks
  • Rexolite looks somewhat better

0 200 400 600 800 0 200 400 600 800

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SLIDE 12

Comparing Reflections from all Four Holders

50000 100000 150000 200000 250000 300000 350000 400000 450000 1 2 3 4 Area (a. u.) Cylindrical Teflon

Area Under FEL Reflection Peaks

  • Integrate peaks
  • Greater area = more reflections

Cylindrical Rexolite Double Cone Teflon Double Cone Rexolite

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SLIDE 13

Conclusions and Future Tests

Conclusions:

  • Rexolite is a better material than Teflon
  • Continue using the cylindrical design for now

Further Testing:

  • Add sample to the holders, measure decay of spins
  • Look for a decrease in “dead-time”
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SLIDE 14

Acknowledgements

  • Devin T. Edwards
  • Dr. Mark S. Sherwin
  • Tyler Shropshire
  • Dr. Arica Lubin