What Factors Influence the Lifetimes of He S=1,0 States in Quantum Mechanics?

[Sekonda]

Hey,

I have question on Helium with one electron in it's ground state orbital 1s and the other in the 2s orbital. We have S=1 states referring to the spin symmetric triplet state and S=0 referring to the spin antisymmetric singlet state, due to quantum effects of the electron-electron interactions we find that the energy of S=1 state and S=0 states are split by the direct and exchange components of the energy correction.

We find that S=1 states, where the spins are parallel, have lower energies than S=0 states - not sure of the physical interpretation of this - I'm guessing it's just because it's energetically favourable to have parallel spins further apart than having opposing spins in the same orbital.

Anyway, the S=1 states and S=0 states have very different lifetimes but I'm not sure what is meant by 'lifetimes' and why the lifetimes are different?

Thanks for any help,
SK

 

[andrien]

there is an energy part due to spins containing S1.S2 which will give negative contribution to energy when spins are parallel and opposite for other.Can you tell where you have seen the lifetimes for them?(it is meant to be for decay)

 

[ycheff]

Phys.Rev. 180 (69) 25-32
Phys.Rev.Lett. 26 (71) 681-684

2³S₁ -> 1¹S₀ t=8000 sec
2¹S₀ -> 1¹S₀ t=19.5 msec

 

[andrien]

Have you seen it is for helium ion,it's o.k. for them.

 

[ycheff]

I don't know value for helium ion, for hydrogen atom:
2²S_1/2 -> 1²S_1/2 t= 2 msec

 

[andrien]

I don't know value for helium ion, for hydrogen atom:

I said that values are for helium ion,not for helium atom.

 

[ycheff]

Hydrogen atom (H I) is analog of helium ion (He II).
For He II:
2²S_1/2 -> 1²S_1/2 t > 1 msec (Bull. Amer. Phys. Soc, 1962, v. 7, p. 258)

 

[andrien]

Oh no,I said For one electron atom it is useful.They are not for two electron atom as is helium atom.You seem to be more interested than O.P.