Triplet and Singlet Helium States

In summary, the conversation discussed the lower energy and shorter lifetime of the spin triplet S=1 state of helium in the 1s2s state due to the exchange interaction. It was clarified that the 1s2s state can be a singlet or a triplet, and both states have long lifetimes as there are no strong transitions to the ground state.
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I have a theoretical question, I just recently learned that the spin triplet S=1 of helium in the state 1s2s is lower in energy than the 1s2 state due to the exchange interaction. I then learned that this 1s2s state has a shorter lifetime than the 1s2 state, can anyone explain why this occurs?

Thanks, John
 
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Jdraper said:
I have a theoretical question, I just recently learned that the spin triplet S=1 of helium in the state 1s2s is lower in energy than the 1s2 state due to the exchange interaction. I then learned that this 1s2s state has a shorter lifetime than the 1s2 state, can anyone explain why this occurs?

Thanks, John
This is not correct. The 1s^2 state (1^S_0) is the ground electronic state. The 1s2s state can be a singlet (2 1^S) or a triplet (2 3^S), depending upon whether the spins are parallel or antiparallel. The 1s2s triplet state and the 1s2s singlet state will be long-lived because they do not have strong (one-photon, electric dipole allowed) transisitons to the ground state.

c.f. http://scholar.uwindsor.ca/cgi/viewcontent.cgi?article=1060&context=physicspub has some discussion of excited He-like atoms
 
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Ok, thanks for clearing that up :)
 

1. What are the triplet and singlet helium states?

The triplet and singlet helium states refer to the different energy levels or electronic configurations of the helium atom. In the triplet state, the two electrons in the helium atom have parallel spins, while in the singlet state, the two electrons have opposite spins.

2. How are the triplet and singlet helium states important in chemistry?

The triplet and singlet states have different electron configurations, which affect the chemical and physical properties of helium. This is particularly important in reactions involving helium, as the different states can have different reactivity and stability.

3. How do the triplet and singlet helium states differ in terms of energy?

The triplet state has a lower energy level than the singlet state. This is due to the parallel spin arrangement of the electrons in the triplet state, which has a lower energy compared to the singlet state where the electrons have opposite spins.

4. What is the significance of the triplet and singlet helium states in quantum mechanics?

The triplet and singlet states are important in understanding the quantum mechanical behavior of electrons in atoms. They demonstrate the concept of spin and how it affects the energy levels and properties of atoms.

5. Can the triplet and singlet helium states be observed in experiments?

Yes, the triplet and singlet states can be observed in experiments using spectroscopy techniques. By analyzing the emitted or absorbed light from a helium atom, scientists can determine the energy levels and configurations of the electrons, including the triplet and singlet states.

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