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	lots of lectures. Class is now over.
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|                         Exam 2 Problem 2 | ||||
| ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ | ||||
| 
 | ||||
| (pic) Finished the problem using the boundary conditions | ||||
| 
 | ||||
|     boundary conditions limit the number of possible spherical harmonics. | ||||
| 
 | ||||
| 
 | ||||
| 
 | ||||
|                         Two Similar Particles | ||||
| ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ | ||||
| 
 | ||||
| ❙a,b❭ = ❙a❭⊗❙b❭ | ||||
| 
 | ||||
|                             Exchange Operator | ||||
| ────────────────────────────────────────────────────────────────────────── | ||||
| 
 | ||||
| 𝓟₁₂❙a,b❭ = ❙a,b❭ | ||||
| 
 | ||||
| 𝓟₁₂(❙a❭⊗❙b❭) = ❙b❭⊗❙a❭ | ||||
| 
 | ||||
| If particles are indistinguishable  | ||||
| 
 | ||||
| 𝓟₁₂❙a,b❭ = exp(iδ) ❙a,b❭ = λ ❙a,b❭ | ||||
| 
 | ||||
| 𝓟²₁₂❙a,b❭ = λ² ❙a,b❭ = ❙a,b❭ ⇒ λ=±1 | ||||
| 
 | ||||
| 
 | ||||
|                             Symmetry States | ||||
| ────────────────────────────────────────────────────────────────────────── | ||||
| (pic) Two cases: symmetric, antisymmetric | ||||
| 
 | ||||
| Symmetric States, λ=1 | ||||
| 
 | ||||
|     𝓟₁₂❙a,b❭ | ||||
| 
 | ||||
| (pic) Constructed the exchange operator in matrix form, then found eigen states | ||||
| 
 | ||||
| (pic) Showed that the exchange operator leads to the Pauli Exclusion Principle | ||||
| 
 | ||||
| 
 | ||||
| 
 | ||||
| 
 | ||||
							
								
								
									
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|                           Two Spin-½ Particles | ||||
| ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ | ||||
| uncoupled basis | ||||
| ─────────────── | ||||
| ❙s₁ s₂ m₁ m₂❭ | ||||
| ❙+ +❭, ❙- -❭, ❙+ -❭, ❙- +❭  | ||||
| 
 | ||||
| coupled basis | ||||
| ───────────── | ||||
| ❙S Mₛ❭ | ||||
| ❙1 1❭, ❙1 -1❭, ❙1 0❭, ❙0 0❭ | ||||
| 
 | ||||
| Given the state ❙1 0❭ = 1/√2(❙+ -❭ + ❙- +❭) : | ||||
|     P₁₂❙1 0❭ = ❙1 0❭ (symmetric) | ||||
| 
 | ||||
| ❙0 0❭ = 1/√2(❙+ -❭ - ❙- +❭) : | ||||
|     P₁₂❙0 0❭ = -❙0 0❭ (antisymmetric) | ||||
| 
 | ||||
| 
 | ||||
|                          Spatial Representation | ||||
| ────────────────────────────────────────────────────────────────────────── | ||||
| ❙Ψ❭ = ❙Ψₛₚₐₜᵢₐₗ❭❙Ψₛₚᵢₙ❭ | ||||
| 
 | ||||
| Symmetric: | ||||
| ❙Ψ❭ˢ = ❙Ψₛₚₐₜᵢₐₗ❭ˢ❙Ψₛₚᵢₙ❭ˢ OR ❙Ψₛₚₐₜᵢₐₗ❭ᴬ❙Ψₛₚᵢₙ❭ᴬ | ||||
| 
 | ||||
| Antisymmetric: | ||||
| ❙Ψ❭ᴬ = ❙Ψₛₚₐₜᵢₐₗ❭ᴬ❙Ψₛₚᵢₙ❭ˢ OR ❙Ψₛₚₐₜᵢₐₗ❭ˢ❙Ψₛₚᵢₙ❭ᴬ | ||||
| 
 | ||||
| 
 | ||||
|                               Helium Atom | ||||
| ────────────────────────────────────────────────────────────────────────── | ||||
| Fermions, so overall must be antisymmetric | ||||
| 
 | ||||
| Configuration       Term        Energy | ||||
|     1s²              1s            0 | ||||
|         ❙Ψ❭ = 1/√2 (❙a❭₁ₛ❙b❭₁ₛ + ❙b❭₁ₛ❙a❭₁ₛ)❙0 0❭ | ||||
| 
 | ||||
|     1s²s             3s            1.46 | ||||
|         ❙Ψ❭ = 1/√2(❙a❭₁ₛ❙b❭₁ₛ - ❙b❭₁ₛ❙a❭₁ₛ)❙1 m❭, m=-1,0,1 | ||||
| 
 | ||||
|     1s2s             1s            1.52 | ||||
|         ❙Ψ❭ = 1/√2 (❙a❭₁ₛ❙b❭₁ₛ + ❙b❭₁ₛ❙a❭₁ₛ)❙0 0❭ | ||||
| 
 | ||||
|     1s2p             3pᵒ           ~1.60 | ||||
|         ❙Ψ❭ = 1√2  | ||||
| 
 | ||||
|     1s²p             1pᵒ           ~1.65 | ||||
| 
 | ||||
|      | ||||
							
								
								
									
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| ∮𝐁⋅d𝐥 = B(s) sπs = μ₀[∫𝐉⋅n̂da + ε₀ d/dt ∫𝐄⋅n̂da] | ||||
| 
 | ||||
| ∫𝐉⋅n̂da = 0 | ||||
| 
 | ||||
| For capacitor: | ||||
| │𝐄│ = σ/ε₀ ⇒ B(s) 2πs = μ₀ ε₀ d/dt σ(t)/ε₀ πs² | ||||
							
								
								
									
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| S𝓍 ≐ ħ͟⎛0 1⎞ | ||||
|      2⎝1 0⎠ | ||||
| 
 | ||||
| Diagonalize the matrix... | ||||
| 
 | ||||
| First, find the characteristic equation and solve for the eigenvalues. | ||||
| 
 | ||||
| S𝓍 ≐ ħ͟⎛0 1⎞ | ||||
|      2⎝1 0⎠ | ||||
| 
 | ||||
| ħ͟ ⎛-λ  1⎞ | ||||
| 2 ⎝ 1 -λ⎠ | ||||
| 
 | ||||
|     λ² - ħ²/4 = 0  | ||||
|     λ² = ħ²/4  | ||||
| 
 | ||||
|     λ = ±ħ/2  | ||||
| 
 | ||||
| So the eigenvalues are those expected for the measurement of a spin-1/2 component. | ||||
| 
 | ||||
| The eigenvalue equations are | ||||
| 
 | ||||
| S𝓍❙Ψ❭ = λ❙Ψ❭ | ||||
| 
 | ||||
| which is represented by | ||||
| 
 | ||||
| ħ͟⎛0 1⎞⎛a⎞ = λ⎛a⎞ | ||||
| 2⎝1 0⎠⎝b⎠    ⎝b⎠ | ||||
| 
 | ||||
| 
 | ||||
							
								
								
									
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| After the first Stern-Gerlach magnet, the entire wave function will be in a single state: | ||||
| 
 | ||||
| ❙Ψ₁❭ = ❙S₊❭  | ||||
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