Clarification of notation

AxiomOfChoice

I'm trying to decipher exactly what it means to say the following things:

(1) The ground electronic state of NO[itex]_2[/itex] is [itex]^{2}A_1[/itex];

(2) The ground electronic state of ClO[itex]_2[/itex] is [itex]^{2}B_1[/itex];

(3) The ground electronic state of O[itex]_2[/itex] is [itex]^{3}\Sigma^{-}_g[/itex].

I really don't have a clue what these symbols are supposed to mean. Can someone please help?

Borek

Have you checked http://en.wikipedia.org/wiki/Molecular_term_symbol