# Triplet state question

#### MonsieurWise

I am trying to draw a diagram of Helium electron transitions based on its spectrum. I found out some of the transitions have to be explained in Triplet state. I searched on the internet but all I get are equations...(like the one in Wikipedia with weird brackets, like "(" and then ">" ) and talk about dimensions.
Is there any explanation that a high school student like me can understand...? Thank you very much ^^

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#### MonsieurWise

Oh, thank you very much! A great website indeed! It also answer some of my questions...
There are still something I don't understand, but I hope I will after examine the website...
So far, it is mean that "anti-parallel" mean like two electron in the s-orbital that have spin up and spin down, is called "Singlet"? And "parallel" mean like one electron lay in the s-orbital and the other one in p-orbital, both have to have spin-up, thus move in the same direction and lower in energy called "Triplet"? Am I still on track, or I'm lost already...?
Oh, and by the way...Why does the orbital quantum number l contribute to big atom energy level, but do nothing to Hydrogen energy level?
Thank you.

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#### alxm

"anti-parallel" spins are opposite: one up and one down.
"parallel" spins are the same, either up-up or down-down (in the absence of a magnetic field, the two combinations will have the same energy, so the actual orientation isn't important)

A singlet state means all spins are paired and the total spin, S = 0.
A doublet means a single unpaired spin and S=1/2
A triplet means two unpaired (parallel) spins and S = 1.
And so forth.
(In the particular case of Helium, there are also the historic terms 'ortho-helium' for singlet helium and 'para-helium' for triplet helium. )

The Pauli exclusion principle dictates that two electrons cannot be in the same orbital and have the same spin.

Oh, and by the way...Why does the orbital quantum number l contribute to big atom energy level, but do nothing to Hydrogen energy level?
It has just as much to do with hydrogen as with any other atom. I already said in an answer to another one of your posts that the 'n' in the Bohr atomic model is not the 'n' that is the principal quantum number. Are you confusing these again?

#### MonsieurWise

I think I confused these again... but somehow I couldn't remember your earlier post. Could you post it again if you have some time? I couldn't find it anywhere...>.<.
But when I see the energy diagram of Hydrogen compared to Helium, with n as the y-asix in the left and orbital quantum number l (s,p,d...) as the x axis, like in the website
http://hyperphysics.phy-astr.gsu.edu...um/helium.html [Broken]
That Bob gave me, I see the effect of l (s,p,d...) on the level of Helium (either energy go up a bit or down a bit in the same n level), when in Hydrogen level it does not affect at all (all the electron in the same n level have same energy, regardless of l).
So I'm getting more confused...>.<. Could you explain the difference again...?
And could you also explain the 2 term "symmetric" and "anti-symmetric" of the 2 spins?
Am I too demanding...^^'?
Thank you very much

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#### alxm

But when I see the energy diagram of Hydrogen compared to Helium, with n as the y-asix in the left and orbital quantum number l (s,p,d...) as the x axis, like in the website
http://hyperphysics.phy-astr.gsu.edu...um/helium.html [Broken]
That Bob gave me, I see the effect of l (s,p,d...) on the level of Helium (either energy go up a bit or down a bit in the same n level), when in Hydrogen level it does not affect at all (all the electron in the same n level have same energy, regardless of l).
Well, no, they have a different energy depending on l, even in hydrogen, as explained http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/orbdep.html" [Broken] the corresponding diagram (somewhat exaggerated - obviously not to scale) for hydrogen (plus some lines showing possible transitions), with l on the x-axis and everything. The difference between the levels with different l increases with more electrons, this is because of how electrons interact with each other (called spin-orbit coupling).

And could you also explain the 2 term "symmetric" and "anti-symmetric" of the 2 spins?
Well, 'symmetric'/'anti-symmetric' is a description of what what the wave function looks like, or rather, a condition put upon the spatial wave function, which depends on the spin state. It is 'symmetric' if it doesn't change sign (+/-) when you exchange the location of the electrons and 'anti-symmetric' if it does. For a two-electron system, the (spatial) wave function must be symmetric if it's a singlet and anti-symmetric if it's a triplet state.

Am I too demanding...^^'?
No, but the subject is. Remember, it took the world's leading physicists almost 50 years from the discovery of the Balmer series until they'd fully understood the hydrogen spectrum, and they had to completely revolutionize physics by inventing quantum theory to do so! So you really need to learn quantum physics to fully understand what's going on. And that's not something one does overnight.

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Thank you!

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