|
|Section2= |Section5= |Section6= |Section7= }} : ''This article is about the physics of atomic helium. For other properties of helium, see helium.'' A helium atom is an atom of the chemical element helium. Helium is composed of two electrons bound by the electromagnetic force to a nucleus containing two protons along with either one or two neutrons, depending on the isotope, held together by the strong force. Unlike for hydrogen, a closed-form solution to the Schrödinger equation for the helium atom has not been found. However, various approximations, such as the Hartree–Fock method, can be used to estimate the ground state energy and wavefunction of the atom. ==Introduction== The Hamiltonian of helium, considered as a three-body system of two electrons and a nucleus and after separating out the centre-of-mass motion, can be written as : where is the reduced mass of an electron with respect to the nucleus, and are the electron-nucleus distance vectors and . The nuclear charge, is 2 for helium. In the approximation of an infinitely heavy nucleus, we have and the mass polarization term disappears. In atomic units the Hamiltonian simplifies to : The presence of the electron-electron interaction term 1/r12 makes this equation non separable. This means that 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. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「helium atom」の詳細全文を読む スポンサード リンク
|