Spectral dependence of purely-Kerr-driven filamentation in air and argon

5 pags, 4 figs.-- PACS number(s): 42.65.Jx, 42.65.Tg, 78.20.Ci. -- Publisher error corrected 27 September 2010, Erratum Phys. Rev. A 82, 039905 (2010): https://doi.org/10.1103/PhysRevA.82.033826Based on numerical simulations, we show that higher-order nonlinear indices (up to n8 and n10, respectively) of air and argon have a dominant contribution to both focusing and defocusing in the self-guiding of ultrashort laser pulses over most of the spectrum. Plasma generation and filamentation are therefore decoupled. As a consequence, ultraviolet wavelength may not be the optimal wavelength for applications requiring to maximize ionization. © 2010 The American Physical Society.This work was supported by the Conseil Régional de Bourgogne, the ANR COMOC, the FASTQUAST ITN Program of the 7th FP, and the Swiss NSF (Contracts No. 200021-116198 and No. 200021-125315)