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  2. Variational method (quantum mechanics) - Wikipedia

    en.wikipedia.org/wiki/Variational_method...

    The expectation value of the total Hamiltonian H (including the term V ee) in the state described by ψ 0 will be an upper bound for its ground state energy. V ee is −5E 1 /2 = 34 eV, so H is 8E 1 − 5E 1 /2 = −75 eV. A tighter upper bound can be found by using a better trial wavefunction with 'tunable' parameters.

  3. Ground state - Wikipedia

    en.wikipedia.org/wiki/Ground_state

    The ground state of a quantum-mechanical system is its stationary state of lowest energy; the energy of the ground state is known as the zero-point energy of the system. An excited state is any state with energy greater than the ground state. In quantum field theory, the ground state is usually called the vacuum state or the vacuum. If more ...

  4. Atomic electron transition - Wikipedia

    en.wikipedia.org/wiki/Atomic_electron_transition

    The energy of an electron is determined by its orbit around the atom, The n = 0 orbit, commonly referred to as the ground state, has the lowest energy of all states in the system. In atomic physics and chemistry , an atomic electron transition (also called an atomic transition, quantum jump, or quantum leap) is an electron changing from one ...

  5. Hund's rules - Wikipedia

    en.wikipedia.org/wiki/Hund's_rules

    One of these electrons must have, (for some chosen direction z) m s = 1 ⁄ 2, and the other must have m s = − 1 ⁄ 2. Hund's first rule states that the lowest energy atomic state is the one that maximizes the total spin quantum number for the electrons in the open subshell. The orbitals of the subshell are each occupied singly with ...

  6. Multiplicity (chemistry) - Wikipedia

    en.wikipedia.org/wiki/Multiplicity_(chemistry)

    When S > L there are only 2L+1 orientations of total angular momentum possible, ranging from S+L to S-L. [2] [3] The ground state of the nitrogen atom is a 4 S state, for which 2S + 1 = 4 in a quartet state, S = 3/2 due to three unpaired electrons. For an S state, L = 0 so that J can only be 3/2 and there is only one level even though the ...

  7. Hund's rule of maximum multiplicity - Wikipedia

    en.wikipedia.org/wiki/Hund's_Rule_of_Maximum...

    The manganese (Mn) atom has a 3d 5 electron configuration with five unpaired electrons all of parallel spin, corresponding to a 6 S ground state. [4] The superscript 6 is the value of the multiplicity , corresponding to five unpaired electrons with parallel spin in accordance with Hund's rule.

  8. Excited state - Wikipedia

    en.wikipedia.org/wiki/Excited_state

    Atoms can be excited by heat, electricity, or light. The hydrogen atom provides a simple example of this concept.. The ground state of the hydrogen atom has the atom's single electron in the lowest possible orbital (that is, the spherically symmetric "1s" wave function, which, so far, has been demonstrated to have the lowest possible quantum numbers).

  9. Intersystem crossing - Wikipedia

    en.wikipedia.org/wiki/Intersystem_crossing

    That is, the spin of the excited electron is still paired with the ground state electron (a pair of electrons in the same energy level must have opposite spins, per the Pauli exclusion principle). In a triplet state the excited electron is no longer paired with the ground state electron; that is, they are parallel (same spin). Since excitation ...