# P orbital notation

by Hypersphere
Tags: notation, orbital
 P: 184 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?