  We measure the nonlinear refractive index coefficients in N$_2$, O$_2$ and Ar
from visible through mid-infrared wavelengths (\lambda = 0.4 - 2.4 {\mu}m). The
wavelengths investigated correspond to transparency windows in the atmosphere.
Good agreement is found with theoretical models of $\chi^{(3)}$. Our results
are essential for accurately simulating the propagation of ultrashort mid-IR
pulses in the atmosphere.
