P Orbital Notation: Common Conventions

[Hypersphere]

Hi,

Reading http://rmp.aps.org/abstract/RMP/v70/i4/p1039_1 I've run into a notational question of atomic p orbitals. The authors use symbols like $p_\sigma$ and $p_\pi$. From their fig. 3 (attached), they do look like $p_x$ and $p_z$ orbitals, respectively, rather than anything close to σ or π bonds.

Is this just a common notational convention that I've somehow missed? And if so, what is the symbol for the third p orbital?

 

[DrDu]

Where's the figure?

 

[Hypersphere]

Here it is, I hope...

 

[DrClaude]

They are the indeed $p_x$ and $p_z$orbitals. My guess is that they are using this notation to signify that the bond formed will be a $\sigma$ or $\pi$ bond.

 

[Hypersphere]

Ah! Now that makes some sense. Thank you.