Establish from which initial states of the pp system amongst ¹S₀, ³S₁, ¹P₁, ³P₀, ³P₁, ³P₂, ¹D₂, ³D₁, ³D₂ and ³D₃ the reaction p̅p → nπ° can proceed with parity conservation:

(1) for any n; 

(2) for n=2.