Equation Icon  ----- 2κ ∘ 2w2 Ψ (r,z) = -2- ---- exp(− itan−1(z∕zR )) bf π ∫ b∕w [ ] exp − Z (r∕w − x )2 exp(− 2Zrx ∕w )I0(2Zrx ∕w )xdx. (2.9 ) 0