FIG. 10.

The difference of the nonlinear susceptibility as a function of radial position is given for several initial field strengths in units of kV/m. The incident electric field follows $E(\rho )=E_0{e}^{-{\left(\rho /w_0\right)}^2}$. The dashed vertical lines indicate the radial position for which the incident field has fallen by a given factor. The black dots are the points used to evaluate the series given in Eqs. (26)–(28).