We show by explicit calculation of our previously published quasicontinuum model that the molecular susceptibility rapidly approaches zero as higher excited states of the molecule become populated. Hence the overtones of the ν3-pumped mode are totally responsible for the self tocusing effects in SF6. We explicitly calculate the ν3 ladder contribution to the susceptibility. Our vibrational model is a classical triply degenerate anharmonic oscillator in the Cartesian basis with the anharmonicity parameters chosen to be consistent with the latest spectroscopic analysis of the 3ν3 overtone spectrum. The rotational struc-ture is represented by a distribution of these oscillators where the distribution is chosen to correspond to the spectrum of the ν3 fundamental. We find good agreement with the 300K self-focusing data of Nowak and Ham at CO2 P(28), P(20) and P(10) in SF6.