constant[3], c is the speed of light and is approximately equal to 137a.u.. The angular factor such as f ( θ 0 , φ 0 ; θ$_{L}$, φ$_{L}$ ) represents the dependence of the detached-electron wave function on the outgoing direction ( θ 0 , φ 0 ) for center 0, and it can be written as [25] The angular factors f ( θ 1 , φ 1 ; θ$_{L}$, φ$_{L}$ ) and f ( θ 2 , φ 2 ; θ$_{L}$, φ$_{L}$ ) can be written out in a similar way. After substituting Eqs.(2) and Eqs.(3) in Eq.(1), we can get the explicit expression for the detached-electron wave function Ψ + $_{M}$. The resulting formula for Ψ + M can be simplified because the calculation of the photodetachment cross section requires the knowledge of Ψ + M at large distances where r 1 , r 0 and r 2 are much greater than the distance d between two neighboring centers. Let ( r, θ, φ ) be the spherical coordinates of the detached-electron relative to the origin. Then we approximate the phase terms using r 1 ≈ r − d cos θ , r 0 = r , r 2 ≈ r + d cos θ ; in other places we can set r 1 ≈ r 2 ≈ r 0 = r , θ 1 ≈ θ 2 ≈ θ 0 = θ . With these approximations, Ψ + M becomes Eq.(4) describes the detached-electron wave of the linear triatomic anion when the detached- electron is far away from the anion. The differential cross section is [5] where σ is the photodetachment cross section, ds is the differential area on a surface Γ such as the surface of a large sphere enclosing the anion, q is the coordinate on the surface Γ, n is the exterior norm vector at q and j is the detached-electron flux. The detached-electron flux in the radial direction can be evaluated as When Eq.(4) is substituted in Eq.(6), we get 4 $^{j}$· ˆ r = 16 B $^{2}$k4 3 k ( k 2 b + k 2 ) 4 f $^{2}$( θ, φ ; θ$_{L}$, φ$_{L}$ ) r 2 [1 + 4 cos( kd cos θ ) + 4 cos $^{2}$( kd cos θ )] . (7) j$_{r}$ ( r, θ, φ ) = $^{j}$· ˆ r = i 2 (Ψ + M ∂ Ψ $^{+}$∗ M ∂r − Ψ $^{+}$∗ M ∂ Ψ + M ∂r ) . (6) dσ ( q ) ds = 2 πE$_{ph}$ c $^{j}$· n , (5) j = i 2 (Ψ + M ∇ Ψ $^{+}$∗ M − Ψ $^{+}$∗ M ∇ Ψ + $_{M}$) , Ψ + $_{M}$( r, θ, φ ) = 4 Bk $^{2}$i ( k 2 b + k 2 ) 2 1 √$_{3}$ f ( θ, φ ; θ$_{L}$, φ$_{L}$ )[1 + 2 cos( kd cos θ )] exp( ikr ) kr , r → ∞ . (4) f ( θ 0 , φ 0 ; θ$_{L}$, φ$_{L}$ ) = cos θ 0 cos( θ$_{L}$ ) + sin θ 0 sin( θ$_{L}$ ) cos( φ 0 − φ$_{L}$ ) . (3)