where D$_{|}$$_{|}$ and D$_{⊥}$ are convergent series of the form D$_{|}$$_{|}$ = − ∑ l 2 $_{x}$( − 1) l$_{x}$ ( l 2 x + l 2 y ) 5 / 2 ∼ = 0 . 6354 , D$_{⊥}$ = ∑ ⃗ l =0 l 2 $_{y}$( − 1) l$_{x}$ ( l 2 x + l 2 y ) 5 / 2 ∼ = 1 . 256 . (29) 30