Electron Spin Resonance in Microwave Field Feng lei

Electron Spin Resonance in Microwave Field Feng lei 06300190031 2020/9/25 1

Outline • Introduction 1. Microwave in waveguide 2. ESR • Microwave in waveguide • DPPH’s ESR in Microwave Field • Conclusion 2020/9/25 2

Introduction • Paulli introduced electron spin in 1924. • ESR was invented by the Russian physicist Zavoisky in 1945. • Extended by a group of physicists at Oxford University in the next decade. • Electron spin resonance spectroscopy (ESR). 2020/9/25 3

Microwave in waveguide • Rectangular waveguide a=23 mm, b=10 mm • Only TE 10 is allowed in this waveguide when the frequency of Microwave is 9. 845 GHz. 2020/9/25 4

Electron spin • Electrons also have spin as nucleus: • When in magnetic field: • Resonance absorption condition: 2020/9/25 5

Susceptibility • Physics view: a spin electron ≈ a magnetic dipole • Radioactive field: • So macro-absorption is proportional to χ 2020/9/25 6

Bloch equation • Relaxation time approximation • where γ = -28. 06 GHz/T, and • So dynamic susceptibility: 2020/9/25 7

Microwave in waveguide • Shorting piston Max-Position(mm) Min-Position(mm) VSWR 78. 02 88. 7 40 98. 62 109. 0 37. 5 119. 9 129. 42 43 139. 5 149. 97 40 2020/9/25 8

Microwave in waveguide • Attenuator: 2020/9/25 9

Microwave in waveguide • H-T No. 1(measurement) 1(calculation) 2(measurement) 2(calculation) • E-T 1 -5. 2 m. W -1 W 1. 5 m. W (28. 8%) 0. 242 W (24. 2%) No. 1(measurement) 1 -5. 2 m. W 1(calculation) -1 W 2(measurement) 1. 95 m. W (37. 5%) 0. 416 W (41. 6%) 2(calculation) 2020/9/25 2 1. 7 m. W (32. 7%) 0. 281 W (28. 1%) -5. 2 m. W -1 W 2 1. 7 m. W (32. 6%) 0. 438 W (28. 1%) -5. 2 m. W -1 W 3 1. 7 m. W (32. 7%) 0. 281 W (28. 1%) 3. 5 m. W (67. 3%) 0. 673 W (67. 3%) 3 1. 7 m. W (32. 6%) 0. 438 W (28. 1%) 2. 20 m. W (42. 3%) 0. 569 W (56. 9%) Simulation 10

Microwave in waveguide • M-T No. 1 1(measurement) -5. 2 m. W 1(calculation) 2(measurement) 2(calculation) 3(measurement) 3(calculation) 2020/9/25 2 3 4 Simulation 1. 79 m. W 0 m. W (34. 4%) -1 W 0. 315 W 0. 303 W 0. 00307 W (31. 5) (30. 3%) (0. 3%) 1. 7 m. W -5. 2 m. W 1. 12 m. W 2. 22 m. W (32. 7%) (21. 5%) (42. 7%) 0. 275 W -1 W 0. 254 W 0. 458 W (32. 3%) (25. 4%) (45. 8%) 0 m. W 2. 08 m. W -5. 2 m. W (40%) 0. 002624 W 0. 413 W 0. 487 W -1 W (0. 26%) (41. 3%) (48. 7%) 11

Microwave in waveguide • Expand with plane wave 2020/9/25 12

Microwave in waveguide • Why it is so magic? Power flow Bx 2020/9/25 Ey By Ez Bz 13

ESR • Experiment system 2020/9/25 14

ESR • Signal 2020/9/25 15

ESR • Image Processing • For resonator: 2020/9/25 16

ESR Signal First derivative Second derivative • Slope ratio of first derivative of peaks No. B/A 1 1. 06 4. 48 2 3. 15 3 0. 789 6. 81 • Theoretic B/A: Lorentz 4 Gauss 2. 2 2020/9/25 17

ESR • Mixed Curve 2020/9/25 18

ESR • If this interpretation is right: • This dissipation is fractional but important. 2020/9/25 19

Conclusion • Measurement and Simulation of Transmission efficiency of attenuator, M-T, H-T, E-T. • Measurement of constant of TE 10 in rectangular wave guide. • ESR of DPPH in microwave field. • ESR image processing and argument of absorption curve type. 2020/9/25 20

Thanks for your attention 2020/9/25 21