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1 | 1 | ## Hydrogenlike atoms
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2 | 2 |
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3 |
| -```{admonition} What you need to know |
| 3 | +:::{admonition} **What you need to know** |
| 4 | + |
4 | 5 | :class: note
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5 |
| -- Hydrogen atom is the simplest atom for which Schrodinger equation can be solved exactly. He atom which only has one more electron already proves to be impossible to solve exactly. |
6 |
| -- The solution of the Schrödinger equation for H atom uses the fact that the Coulomb potential produced by the nucleus is isotropic: it is radially symmetric in space and only depends on the distance to the nucleus. This symmetry gives rise to degenercaies in energy levels. |
7 |
| -- Although the resulting energy eigenfunctions (the orbitals) are not necessarily isotropic themselves, their dependence on the angular coordinates follows completely generally from this isotropy of the underlying potential. |
8 |
| -- The angular momentum is conserved, therefore, the energy eigenvalues may be classified by two angular momentum quantum numbers, ℓ and m (both are integers) and quantize mangitude and projection of angular momentum. |
9 |
| -- Atomic orbitals are introduced which are used for also describing multi-electron atoms and molecules. |
10 |
| -``` |
| 6 | + |
| 7 | +- The **hydrogen atom** is the simplest atom for which the Schrödinger equation can be solved exactly. In contrast, helium—though only having one additional electron—cannot be solved exactly due to the complexity introduced by electron-electron interactions. |
| 8 | +- Solving the Schrödinger equation for the hydrogen atom leverages the fact that the **Coulomb potential from the nucleus is isotropic**: it is radially symmetric and depends solely on the distance from the nucleus. This **symmetry leads to degeneracies in the energy levels**. |
| 9 | +- While the resulting energy eigenfunctions (atomic orbitals) are not necessarily isotropic, their dependence on angular coordinates arises fundamentally from the isotropy of the underlying potential. |
| 10 | +- Because angular momentum is conserved, energy eigenvalues can be classified by two angular momentum quantum numbers, $l$ and $m$ (both integers), which quantize the magnitude and projection of angular momentum. |
| 11 | +- **Atomic orbitals** derived for hydrogen are also foundational in describing the structure of multi-electron atoms and molecules. |
| 12 | +::: |
11 | 13 |
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12 | 14 |
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13 | 15 | ### Schrodinger equation for hydrogenlike atoms
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18 | 20 |
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19 | 21 | - We have a porblem of one particle moving in a symmetric potential field in 3D. Expect to get 3 quantum numbers, anticipate some degenreacies due to this raidal symmetry.
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20 | 22 |
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21 |
| -- **Potential energy** operator consists of one coulomb term encoding the electrostatic attraction between nucleus and electron: |
| 23 | +- **Kinetic energy operator** in 3D is the same as in the particle in a box in 3D: |
| 24 | + |
| 25 | +$$\frac{\hbar^2}{2m_e}\nabla^2$$ |
| 26 | + |
| 27 | +- **Potential energy operator** operator consists of one coulomb term encoding the electrostatic attraction between nucleus and electron: |
22 | 28 |
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23 | 29 | $$V= - \frac{Ze^2}{4\pi\epsilon_0 r}$$
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24 | 30 |
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25 | 31 | - Where $m_e$ is the electron mass, $\epsilon_0$ is the [vacuum permitivity](http://en.wikipedia.org/wiki/Vacuum_permittivity).
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26 | 32 |
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27 |
| -- **Kinetic energy operator** in 3D is the same as in the particle in a box in 3D: |
28 |
| -$$\frac{\hbar^2}{2m_e}\nabla^2$$ |
| 33 | + |
29 | 34 |
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30 | 35 |
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31 | 36 |
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32 | 37 | ### H-atom in spherical coordinates system
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33 | 38 |
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34 |
| -- Because of the spherical symmetry of the [Coulomb potential](http://en.wikipedia.org/wiki/Coulomb's_law)it is convenient to work in spherical coordinates: |
| 39 | +- Because of the spherical symmetry of the [Coulomb potential](http://en.wikipedia.org/wiki/Coulomb's_law) it is convenient to work in spherical coordinates: |
35 | 40 |
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36 | 41 |
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37 | 42 | $${\left[ -\frac{\hbar^2}{2m_e}\Delta - \frac{Ze^2}{4\pi\epsilon_0 r}\right]\psi_i(r,\theta,\phi) = E_i\psi(r,\theta,\phi)}$$
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@@ -78,14 +83,16 @@ $$V_{eff} = - \frac{Ze^2}{4\pi\epsilon_0r}+ \frac{l(l+1)\hbar^2}{2m_er^2} $$
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78 | 83 |
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79 | 84 | - The eigenvalues $E_{nl}$ and and the radial eigenfunctions $R_{nl}$ can be written as (derivations are lengthy but standard math):
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80 | 85 |
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81 |
| -$${E_{nl} = -\frac{m_ee^4Z^2}{32\pi^2\epsilon_0^2\hbar^2n^2}{ with }n = 1,2,3...{ (independent of }l,l<n{)}}$$ |
| 86 | +$${E_{nl} = -\frac{m_ee^4Z^2}{32\pi^2\epsilon_0^2\hbar^2n^2}{ \,\,\, }n = 1,2,3...{ (independent\, of\, }l,\,\,\,l<n{)}}$$ |
| 87 | + |
| 88 | +$$R_{nl}(r) = \rho^le^{-\rho/2}{L_{n-l-1}^{2l+1}(\rho)}$$ |
82 | 89 |
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83 |
| -$${R_{nl}(r) = \rho^lL^{2l+1}_{n+l}(\rho){exp}\left(-\frac{\rho}{2}\right){ with }\rho = \frac{2Zr}{na_0}{ and } |
84 |
| -a_0 = \frac{4\pi\epsilon_0\hbar^2}{m_ee^2}}$$ |
85 | 90 |
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86 |
| -- where $L_{n+l}^{2l+1}(\rho)$ are [Laguerre polynomials](http://en.wikipedia.org/wiki/Laguerre_polynomials). The constant $a_0$ is called the [Bohr radius](http://en.wikipedia.org/wiki/Bohr_radius). Some of the first radial wavefunctions are listed on the next page.Some of the electronic energy levels of hydrogen atom are shown below. |
| 91 | +- **Bohr radius:** $a_0 = \frac{4\pi\epsilon_0\hbar^2}{m_ee^2}$ |
87 | 92 |
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| 93 | +- **Dimensionless distance defined via ratio of Bohr radius:** $\rho = \frac{2Zr}{na_0}$ |
88 | 94 |
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| 95 | +- **[Laguerre polynomials](http://en.wikipedia.org/wiki/Laguerre_polynomials) $L_{n+l}^{2l+1}(\rho)$** |
89 | 96 |
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90 | 97 | #### Examples of the radial wavefunctions for hydrogenlike atoms
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91 | 98 |
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@@ -121,33 +128,47 @@ $${E_i = R_HZ^2\left(\frac{1}{1^2} - \frac{1}{\infty}\right)}$$
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121 | 128 |
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122 | 129 | ### Quantum numbers $n$, $l$ and $m$
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123 | 130 |
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124 |
| -The quantum numbers in hydrogenlike atoms take on the following values dicated by the solution of Schrodinger equation with boundary conditions imposed respective radial and anuglar parts: |
| 131 | +The quantum numbers in hydrogenlike atoms take on the following values dicated by the solution of Schrodinger equation with boundary conditions imposed respective radial and anuglar parts |
| 132 | + |
| 133 | +:::{admonition} **Quantum numbers of Hydrogen Atom** |
125 | 134 |
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126 | 135 | $${n = 1, 2, 3, ...}$$
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127 | 136 | $${l = 0, 1, 2, ..., n-1}$$
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128 | 137 | $${m = 0, \pm 1, \pm 2,...,\pm l}$$
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| 138 | +$${m_s = \pm 1/2}$$ |
| 139 | +::: |
129 | 140 |
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130 |
| -- For a given value of $n$, the level is $n^2$ times degenerate. |
131 | 141 |
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132 | 142 | - For historical reasons, the following letters are used to express the value of $l$:
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133 | 143 |
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134 | 144 | $${\phantom{{symbo}}l = 0, 1, 2, 3, ...}{{symbol} = s, p, d, f, ...}$$
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135 | 145 |
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136 | 146 |
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137 |
| -- Recall that the wavefunctions for hydrogenlike atoms are $R_{nl}(r)Y_l^m(\theta,\phi)$ with $l < n$. For the first shell we have only one wavefunction: $R_{10}(r)Y_0^0(\theta,\phi)$. This state is usually labeled as $1s$, where 1 indicates the [shell number](http://en.wikipedia.org/wiki/Electron_shell) ($n$) and $s$ corresponds to orbital angular momentum $l$ being zero. For $n = 2$, we have several possibilities: $l = 0$ or $l = 1$. The former is labeled as $2s$. The latter is $2p$ state and consists of three degenerate states: (for example, $2p_x$, $2p_y$, $2p_z$ or $2p_{+1}$, $2p_0$, $2p_{-1}$). In the latter notation the values for $m$ have been indicated as subscripts. |
| 147 | +- For the $n=1$ we have only one wavefunction: $R_{10}(r)Y_0^0(\theta,\phi)$. This state is usually labeled as $1s$, where 1 indicates the [shell number](http://en.wikipedia.org/wiki/Electron_shell) ($n$) and $s$ corresponds to orbital angular momentum $l$ being zero. |
| 148 | +- For $n = 2$, we have several possibilities: $l = 0$ or $l = 1$. The former is labeled as $2s$. The latter is $2p$ state and consists of three degenerate states: (for example, $2p_x$, $2p_y$, $2p_z$ or $2p_{+1}$, $2p_0$, $2p_{-1}$). In the latter notation the values for $m$ have been indicated as subscripts. |
138 | 149 |
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139 |
| -- There is one more quantum number that has not been discussed yet: [Spin quantum number](http://en.wikipedia.org/wiki/Spin_quantum_number) For one-electron systems this can have values $\pm\frac{1}{2}$ (will be discussed in more detail later). In absence of magnetic fields the spin levels are degenerate and therefore the total degeneracy of the levels is $2n^2$. |
| 150 | +- There is one more quantum number that has not been discussed yet: [Spin quantum number](http://en.wikipedia.org/wiki/Spin_quantum_number) $m_s=\pm 1/2$ |
| 151 | + |
| 152 | +- For one-electron systems this can have values $\pm\frac{1}{2}$ (will be discussed in more detail later). In absence of magnetic fields the spin levels are degenerate and therefore the total degeneracy of the levels is $2n^2$. |
140 | 153 |
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141 | 154 | ### Total wave function
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142 | 155 |
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143 | 156 | The total wavefunction for a hydrogenlike atom is ($m$ is usually denoted by $m_l$):
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144 | 157 |
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| 158 | +:::{admonition} |
| 159 | +:class: important: |
| 160 | + |
| 161 | +$${\psi_{n,l,m_l}(r,\theta,\phi) = N_{nl}\cdot R_{nl}(r)\cdot Y_{l, m_l}(\theta,\phi)}$$ |
145 | 162 |
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146 |
| -$${\psi_{n,l,m_l}(r,\theta,\phi) = N_{nl}R_{nl}(r)Y_l^{m_l}(\theta,\phi)}$$ |
| 163 | +$$|n, l, m\rangle$$ |
| 164 | + |
| 165 | +::: |
| 166 | + |
| 167 | +Where the normalization factor is: |
147 | 168 |
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148 | 169 | $${N_{nl} = \sqrt{\left(\frac{2Z}{na_0}\right)^3\frac{(n - l - 1)!}{2n\left[(n + l)!\right]}}}$$
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149 | 170 |
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150 |
| -$$R_{nl}(r) = \rho^le^{-\rho/2}{L_{n-l-1}^{2l+1}(\rho)}$$ |
| 171 | + |
151 | 172 |
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152 | 173 | ### Table of Wavefunctions in cartesian coordinates
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153 | 174 |
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