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氦原子是氦元素的原子. 氦原子的原子核由两个质子和一个或者两个中子组成，中子数的不同对应了不同的同位素. 氦原子核的外围由两个电子组成. 氦原子的结构比氢原子要复杂. 因此通过薛定谔方程无法精确求解氦原子的基态能量.

1.引言
作为一个比较典型的三体问题，构造氦原子的哈密顿必须考虑原子核与两个电子之间以及电子和电子之间的相互作用.
 * $$ H\psi(\vec{r}_1,\, \vec{r}_2) = \Bigg[\sum_{i=1,2}\Bigg(-\frac{\hbar^2}{2\mu} \nabla^2_{r_i} -\frac{Ze^2}{4\pi\epsilon_0 r_i}\Bigg) - \frac{\hbar^2}{M} \nabla_{r_1} \cdot \nabla_{r_2} + \frac{e^2}{4\pi\epsilon_0 r_{12}} \Bigg]\psi(\vec{r}_1,\, \vec{r}_2)$$

其中 $$ \mu = \frac{mM}{m+M}$$ 是电子相对与原子核的约化质量，$$ \vec{r}_1 $$ 和 $$ \vec{r}_2 $$ 是电子和原子和之间的距离矢量. 而 $$ r_{12} = |\vec{r_1} - \vec{r_2}| $$则是两个电子之间的的距离. 对于氦原子来说，原子核的电荷数 $$ Z $$ 是 2. 作为一种近似计算，可以将原子核的质量当作无穷大，即 $$ M = \infty $$，这样约化质量 $$ \mu = m $$，可以简化问题的求解. 而质量极化项：$$ \frac{\hbar^2}{M} \nabla_{r_1} \cdot \nabla_{r_2} $$ 也会消失. 用 原子单位可以将哈密顿简化为：


 * $$ H\psi(\vec{r}_1,\, \vec{r}_2) = \Bigg[-\frac{1}{2}\nabla^2_{r_1} - \frac{1}{2}\nabla^2_{r_2} - \frac{Z}{r_1} - \frac{Z}{r_2} + \frac{1}{r_{12}}\Bigg]\psi(\vec{r}_1,\, \vec{r}_2). $$

The presence of the electron-electron interaction term 1/r12 makes this equation non separable. This means that $$ \psi_0(\vec{r}_1,\, \vec{r}_2) $$ cannot be written as a product of one-electron wave functions and the wave function is entangled. Therefore, measurements cannot be made on one particle without affecting the other. Nevertheless, quite good theoretical descriptions of helium can be obtained within the Hartree–Fock and Thomas–Fermi approximations.

Experiment Data
The data of Helium atom's second ionization energy was retrieved from NIST is -24.587387936(25)eV. This experiment data was given by Kandula and et al. However NIST did not give the experiment data of Helium atom's first ionization energy. It only gave the theory value based on quantum theory. The theoretic value of Helium atom's first ionization energy is -54.41776311(2)eV. So the total helium atom's ground state energy is -79.005151046（45）eV, or -2.90338583(13）a.u.

Superconductivity Hydrogen
In Dec. 1, German physicists of Mark Plank institute annanced that they had sucesses in make sulfue to be higher critical temperature. The critical temperature reach at 191K under 168 Mpa.