  We demonstrate the capability of ab-initio time-dependent R-matrix theory to
obtain accurate harmonic generation spectra of noble-gas atoms at Near-IR
wavelengths between 1200 and 1800 nm and peak intensities up to 1.8 X 10(14)
W/cm(2) . To accommodate the excursion length of the ejected electron, we use
an angular-momentum expansion up to Lmax = 279. The harmonic spectra show
evidence of atomic structure through the presence of a Cooper minimum in
harmonic generation for Kr, and of multielectron interaction through the giant
resonance for Xe. The theoretical spectra agree well with those obtained
experimentally.
