This article summarizesequations in the theory ofquantum mechanics .
A fundamentalphysical constant occurring in quantum mechanics is thePlanck constant ,h . A common abbreviation isħ =h /2π , also known as thereduced Planck constant orDirac constant .
The general form ofwavefunction for a system of particles, each with positionr i and z-component of spinsz i . Sums are over the discrete variablesz , integrals over continuous positionsr .
For clarity and brevity, the coordinates are collected into tuples, the indices label the particles (which cannot be done physically, but is mathematically necessary). Following are general mathematical results, used in calculations.
Property or effect Nomenclature Equation Wavefunction forN particles in 3dr = (r 1 ,r 2 ...r N )sz = (s z 1 ,s z 2 , ...,sz N )In function notation:Ψ = Ψ ( r , s z , t ) {\displaystyle \Psi =\Psi \left(\mathbf {r} ,\mathbf {s_{z}} ,t\right)}
inbra–ket notation :| Ψ ⟩ = ∑ s z 1 ∑ s z 2 ⋯ ∑ s z N ∫ V 1 ∫ V 2 ⋯ ∫ V N d r 1 d r 2 ⋯ d r N Ψ | r , s z ⟩ {\displaystyle |\Psi \rangle =\sum _{s_{z1}}\sum _{s_{z2}}\cdots \sum _{s_{zN}}\int _{V_{1}}\int _{V_{2}}\cdots \int _{V_{N}}\mathrm {d} \mathbf {r} _{1}\mathrm {d} \mathbf {r} _{2}\cdots \mathrm {d} \mathbf {r} _{N}\Psi |\mathbf {r} ,\mathbf {s_{z}} \rangle }
for non-interacting particles:
Ψ = ∏ n = 1 N Ψ ( r n , s z n , t ) {\displaystyle \Psi =\prod _{n=1}^{N}\Psi \left(\mathbf {r} _{n},s_{zn},t\right)}
Position-momentum Fourier transform (1 particle in 3d) Φ = momentum–space wavefunction Ψ = position–space wavefunction Φ ( p , s z , t ) = 1 2 π ℏ 3 ∫ a l l s p a c e e − i p ⋅ r / ℏ Ψ ( r , s z , t ) d 3 r ↿⇂ Ψ ( r , s z , t ) = 1 2 π ℏ 3 ∫ a l l s p a c e e + i p ⋅ r / ℏ Φ ( p , s z , t ) d 3 p n {\displaystyle {\begin{aligned}\Phi (\mathbf {p} ,s_{z},t)&={\frac {1}{{\sqrt {2\pi \hbar }}^{3}}}\int \limits _{\mathrm {all\,space} }e^{-i\mathbf {p} \cdot \mathbf {r} /\hbar }\Psi (\mathbf {r} ,s_{z},t)\mathrm {d} ^{3}\mathbf {r} \\&\upharpoonleft \downharpoonright \\\Psi (\mathbf {r} ,s_{z},t)&={\frac {1}{{\sqrt {2\pi \hbar }}^{3}}}\int \limits _{\mathrm {all\,space} }e^{+i\mathbf {p} \cdot \mathbf {r} /\hbar }\Phi (\mathbf {p} ,s_{z},t)\mathrm {d} ^{3}\mathbf {p} _{n}\\\end{aligned}}} General probability distribution Vj = volume (3d region) particle may occupy,P = Probability that particle 1 has positionr 1 in volumeV 1 with spins z 1and particle 2 has positionr 2 in volumeV 2 with spins z 2 , etc.P = ∑ s z N ⋯ ∑ s z 2 ∑ s z 1 ∫ V N ⋯ ∫ V 2 ∫ V 1 | Ψ | 2 d 3 r 1 d 3 r 2 ⋯ d 3 r N {\displaystyle P=\sum _{s_{zN}}\cdots \sum _{s_{z2}}\sum _{s_{z1}}\int _{V_{N}}\cdots \int _{V_{2}}\int _{V_{1}}\left|\Psi \right|^{2}\mathrm {d} ^{3}\mathbf {r} _{1}\mathrm {d} ^{3}\mathbf {r} _{2}\cdots \mathrm {d} ^{3}\mathbf {r} _{N}\,\!} Generalnormalization condition P = ∑ s z N ⋯ ∑ s z 2 ∑ s z 1 ∫ a l l s p a c e ⋯ ∫ a l l s p a c e ∫ a l l s p a c e | Ψ | 2 d 3 r 1 d 3 r 2 ⋯ d 3 r N = 1 {\displaystyle P=\sum _{s_{zN}}\cdots \sum _{s_{z2}}\sum _{s_{z1}}\int \limits _{\mathrm {all\,space} }\cdots \int \limits _{\mathrm {all\,space} }\;\int \limits _{\mathrm {all\,space} }\left|\Psi \right|^{2}\mathrm {d} ^{3}\mathbf {r} _{1}\mathrm {d} ^{3}\mathbf {r} _{2}\cdots \mathrm {d} ^{3}\mathbf {r} _{N}=1\,\!}
Wave–particle duality and time evolution[ edit ] Non-relativistic time-independent Schrödinger equation[ edit ] Summarized below are the various forms the Hamiltonian takes, with the corresponding Schrödinger equations and forms of wavefunction solutions. Notice in the case of one spatial dimension, for one particle, thepartial derivative reduces to anordinary derivative .
One particle N particlesOne dimension H ^ = p ^ 2 2 m + V ( x ) = − ℏ 2 2 m d 2 d x 2 + V ( x ) {\displaystyle {\hat {H}}={\frac {{\hat {p}}^{2}}{2m}}+V(x)=-{\frac {\hbar ^{2}}{2m}}{\frac {d^{2}}{dx^{2}}}+V(x)} H ^ = ∑ n = 1 N p ^ n 2 2 m n + V ( x 1 , x 2 , ⋯ x N ) = − ℏ 2 2 ∑ n = 1 N 1 m n ∂ 2 ∂ x n 2 + V ( x 1 , x 2 , ⋯ x N ) {\displaystyle {\begin{aligned}{\hat {H}}&=\sum _{n=1}^{N}{\frac {{\hat {p}}_{n}^{2}}{2m_{n}}}+V(x_{1},x_{2},\cdots x_{N})\\&=-{\frac {\hbar ^{2}}{2}}\sum _{n=1}^{N}{\frac {1}{m_{n}}}{\frac {\partial ^{2}}{\partial x_{n}^{2}}}+V(x_{1},x_{2},\cdots x_{N})\end{aligned}}} where the position of particlen isxn .
E Ψ = − ℏ 2 2 m d 2 d x 2 Ψ + V Ψ {\displaystyle E\Psi =-{\frac {\hbar ^{2}}{2m}}{\frac {d^{2}}{dx^{2}}}\Psi +V\Psi } E Ψ = − ℏ 2 2 ∑ n = 1 N 1 m n ∂ 2 ∂ x n 2 Ψ + V Ψ . {\displaystyle E\Psi =-{\frac {\hbar ^{2}}{2}}\sum _{n=1}^{N}{\frac {1}{m_{n}}}{\frac {\partial ^{2}}{\partial x_{n}^{2}}}\Psi +V\Psi \,.} Ψ ( x , t ) = ψ ( x ) e − i E t / ℏ . {\displaystyle \Psi (x,t)=\psi (x)e^{-iEt/\hbar }\,.} There is a further restriction — the solution must not grow at infinity, so that it has either a finiteL 2 -norm (if it is abound state ) or a slowly diverging norm (if it is part of acontinuum ):[ 1] ‖ ψ ‖ 2 = ∫ | ψ ( x ) | 2 d x . {\displaystyle \|\psi \|^{2}=\int |\psi (x)|^{2}\,dx.\,}
Ψ = e − i E t / ℏ ψ ( x 1 , x 2 ⋯ x N ) {\displaystyle \Psi =e^{-iEt/\hbar }\psi (x_{1},x_{2}\cdots x_{N})} for non-interacting particles
Ψ = e − i E t / ℏ ∏ n = 1 N ψ ( x n ) , V ( x 1 , x 2 , ⋯ x N ) = ∑ n = 1 N V ( x n ) . {\displaystyle \Psi =e^{-i{Et/\hbar }}\prod _{n=1}^{N}\psi (x_{n})\,,\quad V(x_{1},x_{2},\cdots x_{N})=\sum _{n=1}^{N}V(x_{n})\,.}
Three dimensions H ^ = p ^ ⋅ p ^ 2 m + V ( r ) = − ℏ 2 2 m ∇ 2 + V ( r ) {\displaystyle {\begin{aligned}{\hat {H}}&={\frac {{\hat {\mathbf {p} }}\cdot {\hat {\mathbf {p} }}}{2m}}+V(\mathbf {r} )\\&=-{\frac {\hbar ^{2}}{2m}}\nabla ^{2}+V(\mathbf {r} )\end{aligned}}} where the position of the particle isr = (x, y, z ).
H ^ = ∑ n = 1 N p ^ n ⋅ p ^ n 2 m n + V ( r 1 , r 2 , ⋯ r N ) = − ℏ 2 2 ∑ n = 1 N 1 m n ∇ n 2 + V ( r 1 , r 2 , ⋯ r N ) {\displaystyle {\begin{aligned}{\hat {H}}&=\sum _{n=1}^{N}{\frac {{\hat {\mathbf {p} }}_{n}\cdot {\hat {\mathbf {p} }}_{n}}{2m_{n}}}+V(\mathbf {r} _{1},\mathbf {r} _{2},\cdots \mathbf {r} _{N})\\&=-{\frac {\hbar ^{2}}{2}}\sum _{n=1}^{N}{\frac {1}{m_{n}}}\nabla _{n}^{2}+V(\mathbf {r} _{1},\mathbf {r} _{2},\cdots \mathbf {r} _{N})\end{aligned}}} where the position of particlen isr n = (xn ,yn ,zn ), and the Laplacian for particlen using the corresponding position coordinates is
∇ n 2 = ∂ 2 ∂ x n 2 + ∂ 2 ∂ y n 2 + ∂ 2 ∂ z n 2 {\displaystyle \nabla _{n}^{2}={\frac {\partial ^{2}}{{\partial x_{n}}^{2}}}+{\frac {\partial ^{2}}{{\partial y_{n}}^{2}}}+{\frac {\partial ^{2}}{{\partial z_{n}}^{2}}}}
E Ψ = − ℏ 2 2 m ∇ 2 Ψ + V Ψ {\displaystyle E\Psi =-{\frac {\hbar ^{2}}{2m}}\nabla ^{2}\Psi +V\Psi } E Ψ = − ℏ 2 2 ∑ n = 1 N 1 m n ∇ n 2 Ψ + V Ψ {\displaystyle E\Psi =-{\frac {\hbar ^{2}}{2}}\sum _{n=1}^{N}{\frac {1}{m_{n}}}\nabla _{n}^{2}\Psi +V\Psi } Ψ = ψ ( r ) e − i E t / ℏ {\displaystyle \Psi =\psi (\mathbf {r} )e^{-iEt/\hbar }} Ψ = e − i E t / ℏ ψ ( r 1 , r 2 ⋯ r N ) {\displaystyle \Psi =e^{-iEt/\hbar }\psi (\mathbf {r} _{1},\mathbf {r} _{2}\cdots \mathbf {r} _{N})} for non-interacting particles
Ψ = e − i E t / ℏ ∏ n = 1 N ψ ( r n ) , V ( r 1 , r 2 , ⋯ r N ) = ∑ n = 1 N V ( r n ) {\displaystyle \Psi =e^{-i{Et/\hbar }}\prod _{n=1}^{N}\psi (\mathbf {r} _{n})\,,\quad V(\mathbf {r} _{1},\mathbf {r} _{2},\cdots \mathbf {r} _{N})=\sum _{n=1}^{N}V(\mathbf {r} _{n})}
Non-relativistic time-dependent Schrödinger equation[ edit ] Again, summarized below are the various forms the Hamiltonian takes, with the corresponding Schrödinger equations and forms of solutions.
One particle N particlesOne dimension H ^ = p ^ 2 2 m + V ( x , t ) = − ℏ 2 2 m ∂ 2 ∂ x 2 + V ( x , t ) {\displaystyle {\hat {H}}={\frac {{\hat {p}}^{2}}{2m}}+V(x,t)=-{\frac {\hbar ^{2}}{2m}}{\frac {\partial ^{2}}{\partial x^{2}}}+V(x,t)} H ^ = ∑ n = 1 N p ^ n 2 2 m n + V ( x 1 , x 2 , ⋯ x N , t ) = − ℏ 2 2 ∑ n = 1 N 1 m n ∂ 2 ∂ x n 2 + V ( x 1 , x 2 , ⋯ x N , t ) {\displaystyle {\begin{aligned}{\hat {H}}&=\sum _{n=1}^{N}{\frac {{\hat {p}}_{n}^{2}}{2m_{n}}}+V(x_{1},x_{2},\cdots x_{N},t)\\&=-{\frac {\hbar ^{2}}{2}}\sum _{n=1}^{N}{\frac {1}{m_{n}}}{\frac {\partial ^{2}}{\partial x_{n}^{2}}}+V(x_{1},x_{2},\cdots x_{N},t)\end{aligned}}} where the position of particlen isxn .
i ℏ ∂ ∂ t Ψ = − ℏ 2 2 m ∂ 2 ∂ x 2 Ψ + V Ψ {\displaystyle i\hbar {\frac {\partial }{\partial t}}\Psi =-{\frac {\hbar ^{2}}{2m}}{\frac {\partial ^{2}}{\partial x^{2}}}\Psi +V\Psi } i ℏ ∂ ∂ t Ψ = − ℏ 2 2 ∑ n = 1 N 1 m n ∂ 2 ∂ x n 2 Ψ + V Ψ . {\displaystyle i\hbar {\frac {\partial }{\partial t}}\Psi =-{\frac {\hbar ^{2}}{2}}\sum _{n=1}^{N}{\frac {1}{m_{n}}}{\frac {\partial ^{2}}{\partial x_{n}^{2}}}\Psi +V\Psi \,.} Ψ = Ψ ( x , t ) {\displaystyle \Psi =\Psi (x,t)} Ψ = Ψ ( x 1 , x 2 ⋯ x N , t ) {\displaystyle \Psi =\Psi (x_{1},x_{2}\cdots x_{N},t)} Three dimensions H ^ = p ^ ⋅ p ^ 2 m + V ( r , t ) = − ℏ 2 2 m ∇ 2 + V ( r , t ) {\displaystyle {\begin{aligned}{\hat {H}}&={\frac {{\hat {\mathbf {p} }}\cdot {\hat {\mathbf {p} }}}{2m}}+V(\mathbf {r} ,t)\\&=-{\frac {\hbar ^{2}}{2m}}\nabla ^{2}+V(\mathbf {r} ,t)\\\end{aligned}}} H ^ = ∑ n = 1 N p ^ n ⋅ p ^ n 2 m n + V ( r 1 , r 2 , ⋯ r N , t ) = − ℏ 2 2 ∑ n = 1 N 1 m n ∇ n 2 + V ( r 1 , r 2 , ⋯ r N , t ) {\displaystyle {\begin{aligned}{\hat {H}}&=\sum _{n=1}^{N}{\frac {{\hat {\mathbf {p} }}_{n}\cdot {\hat {\mathbf {p} }}_{n}}{2m_{n}}}+V(\mathbf {r} _{1},\mathbf {r} _{2},\cdots \mathbf {r} _{N},t)\\&=-{\frac {\hbar ^{2}}{2}}\sum _{n=1}^{N}{\frac {1}{m_{n}}}\nabla _{n}^{2}+V(\mathbf {r} _{1},\mathbf {r} _{2},\cdots \mathbf {r} _{N},t)\end{aligned}}} i ℏ ∂ ∂ t Ψ = − ℏ 2 2 m ∇ 2 Ψ + V Ψ {\displaystyle i\hbar {\frac {\partial }{\partial t}}\Psi =-{\frac {\hbar ^{2}}{2m}}\nabla ^{2}\Psi +V\Psi } i ℏ ∂ ∂ t Ψ = − ℏ 2 2 ∑ n = 1 N 1 m n ∇ n 2 Ψ + V Ψ {\displaystyle i\hbar {\frac {\partial }{\partial t}}\Psi =-{\frac {\hbar ^{2}}{2}}\sum _{n=1}^{N}{\frac {1}{m_{n}}}\nabla _{n}^{2}\Psi +V\Psi } This last equation is in a very high dimension,[ 2] so the solutions are not easy to visualize.
Ψ = Ψ ( r , t ) {\displaystyle \Psi =\Psi (\mathbf {r} ,t)} Ψ = Ψ ( r 1 , r 2 , ⋯ r N , t ) {\displaystyle \Psi =\Psi (\mathbf {r} _{1},\mathbf {r} _{2},\cdots \mathbf {r} _{N},t)}
Quantum uncertainty [ edit ] Property or effect Nomenclature Equation Angular momentum quantum numbers Spin:‖ s ‖ = s ( s + 1 ) ℏ m s ∈ { − s , − s + 1 ⋯ s − 1 , s } {\displaystyle {\begin{aligned}&\Vert \mathbf {s} \Vert ={\sqrt {s\,(s+1)}}\,\hbar \\&m_{s}\in \{-s,-s+1\cdots s-1,s\}\\\end{aligned}}\,\!}
Orbital:ℓ ∈ { 0 ⋯ n − 1 } m ℓ ∈ { − ℓ , − ℓ + 1 ⋯ ℓ − 1 , ℓ } {\displaystyle {\begin{aligned}&\ell \in \{0\cdots n-1\}\\&m_{\ell }\in \{-\ell ,-\ell +1\cdots \ell -1,\ell \}\\\end{aligned}}\,\!}
Total:j = ℓ + s m j ∈ { | ℓ − s | , | ℓ − s | + 1 ⋯ | ℓ + s | − 1 , | ℓ + s | } {\displaystyle {\begin{aligned}&j=\ell +s\\&m_{j}\in \{|\ell -s|,|\ell -s|+1\cdots |\ell +s|-1,|\ell +s|\}\\\end{aligned}}\,\!}
Angular momentum magnitudesangular momementa:S = Spin,L = orbital,J = total Spin magnitude:| S | = ℏ s ( s + 1 ) {\displaystyle |\mathbf {S} |=\hbar {\sqrt {s(s+1)}}\,\!}
Orbital magnitude:| L | = ℏ ℓ ( ℓ + 1 ) {\displaystyle |\mathbf {L} |=\hbar {\sqrt {\ell (\ell +1)}}\,\!}
Total magnitude:J = L + S {\displaystyle \mathbf {J} =\mathbf {L} +\mathbf {S} \,\!}
| J | = ℏ j ( j + 1 ) {\displaystyle |\mathbf {J} |=\hbar {\sqrt {j(j+1)}}\,\!}
Angular momentum componentsSpin:S z = m s ℏ {\displaystyle S_{z}=m_{s}\hbar \,\!}
Orbital:L z = m ℓ ℏ {\displaystyle L_{z}=m_{\ell }\hbar \,\!}
Magnetic moments In what follows,B is an applied external magnetic field and the quantum numbers above are used.