Scaling of wave-packet dynamics in an intense midinfrared field

A theoretical investigation is presented that examines the wavelength scaling from near-visible (0.8 mu m) to midinfrared (2 mu m) of the photoelectron distribution and high harmonics generated by a “single” atom in an intense electromagnetic field. The calculations use a numerical solution of the time-dependent Schrodinger equation (TDSE) in argon and the strong-field approximation in helium. The scaling of electron energies (lambda(2)), harmonic cutoff (lambda(2)), and attochirp (lambda(-1)) agree with classical mechanics, but it is found that, surprisingly, the harmonic yield follows a lambda(-(5-6)) scaling at constant intensity. In addition, the TDSE results reveal an unexpected contribution from higher-order returns of the rescattering electron wave packet.