Optical Pumping I’M SO PUMPED FOR THIS!!! I also am quite excited By David Ray

1 Introduction What am I presenting?

Historical Background Discovered By Alfred Kastler Led to the development of lasers Awarded Nobel Prize in 1966

Caesium: 1s22s22p63s23p63d104s24p64d105s25p66s1 Angular Momentum Caesium: 1s22s22p63s23p63d104s24p64d105s25p66s1 [Xe]6s1 F=5 F=4 F=3 (I=7/2) 6s1/2 6p3/2 6p1/2 6s 6p L S J I F Fine structure Hyperfine structure

Zeeman Effect Hyperfine structure mF =-F,-F+1,…,F Zeeman mF=1 mF F ΔEF ΔEF = gF µB |B| mF (gF=1/4)

Pumping Right circularly polarised light imposes absorption selection rule mF=+1 Spontaneous emission selection rule mF=-1,0,1 F=1 p1/2 No available transiton i.e. atom’s “Pumped” -1 mF 1 F=1 s1/2 Zeeman

Transitions Spontaneous Emission Stimulated Emission ΔE Photon approaches electron Electron’s in excited state Photon’s absorbed Photon matching ΔE approaches electron Spontaneous emission Stimulated emission Photon approaches Excited state Ground state Excited state Electron emits photon in random direction Stimulates emission of photon

Rabi Oscillations Population is the percentage of electrons in a given state Rabi oscillations are the fluctuations of the population with respect to time Stimulated emission Absorption Stimulated emission System is “Pumped” Stimulated emission Stimulated emission P(ground) ∝ sin2( ωt/2) P(ground) + P(excited) = 1

2 Methodology How will this be achieved?

(temperature controlled) Equipment Focusing lens RF coil Linear polariser Focusing lens Light rack Caesium Chamber Photo-detector Quarter-wave plate Interference filter Caesium lamp (temperature controlled) Horizontal field & Sweep field http://spa-mxpweb.spa.umn.edu/s11/Projects/S11_OpticalPumping/apparatus.htm

Earth’s Magnetic Field Photorack provides a channel to oscilloscope based on opacity of Caesium Chamber Photorack Oscilloscope Sweeping field & Horizontal Field RF field This is dependant on this equation ΔEF = gF µB |B| mF When B is such a value that hf = gF µB |B| mF Opacity will drop |B| = √(BC+BE||)2 +BE ⊥ 2

Rabi oscillations RF field is periodically turned off Pulse Generator Photorack Oscilloscope Horizontal Field RF field Pulse Generator Plot a curve to fit resulting oscillations

3 Results What was observed?

Earth’s Magnetic Field B/T fres /Hz Plotted fres vs. B By: hf = gF µB √(BC+BE||)2 +BE⊥2 mF A occurs when BE|| =-BC Graphs linear when BE ~0 ∴BE = 50.3± 2.3 µT

Rabi Oscillations ω = 4736 ± 5 Hz Fitted e-at+sin(ωt)+c ω corresponds to Rabi frequency ω = 4736 ± 5 Hz

4 Conclusion What does this all mean?