# The concept of parity and it's significance

1. Apr 10, 2013

### Leb

Hi,

I am revising my intro to nuclear physics class and was wondering why is parity so important ?
I mean OK, I get it, physicists are crazy about symmetries, but I do not understand what does it physically mean...

I was wondering if someone could possibly talk me through its importance and maybe some "deeper" meaning ?

For example, what would 15 Oxygen having a ground state with odd (-1) parity mean ? Would this parity reflect somehow on the chemical properties ?

The rules for parity of a ground state, i.e. P=(-1)^{L}, where do they come from ?

Thanks!

P.S.
Sorry about "it's" in the title, noticed it too late.

2. Apr 10, 2013

### copernicus1

The physical meaning of parity as applied to particles is not something you can easily visualize, but the concept is useful in particle physics because parity conservation (in the strong and EM interactions) constrains the kinds of interactions we expect to see and allows us to make predictions.

It sounds like you may be interested in applying parity to chemistry and chemical interactions, which I'm less familiar with, since I know the concept from particle physics. In particle physics, the parity of a state comes from multiplying the individual intrinsic parities of the particles, and then you do get that $(-1)^\ell$ factor. That last factor comes from the fact that the spatial part of the wave function has a parity associated with it. You can look for a proof, but basically when you let the parity operator operate on a spatial wave function, it hits the spherical harmonic and its eigenvalue is $(-1)^\ell$. That is to say, spherical harmonics of even orbital angular momentum have even parity, and those of odd orbital angular momentum have odd parity.

3. Apr 12, 2013

### Leb

I just read about how parity violation in weak interactions, in particular, example of β-decay of polarised 60 Co. Although I still could not imagine parity as some trait, I think I might see the importance, I almost feel ashamed for my ignorance...