Wavelength scaling of high-harmonic yield: threshold phenomena and bound state symmetry dependence

Describing harmonic generation (HG) in terms of a system's complex quasienergy, the harmonic power P_{DeltaE}(lambda) (over a fixed interval, DeltaE, of harmonic energies) is shown to reproduce the wavelength scaling predicted recently by two groups of authors based on solutions of the time-dependent Schrödinger equation: P_{DeltaE}(lambda) approximately lambda;{-x}, where x approximately 5-6. Oscillations of P_{DeltaE}(lambda) on a fine lambda scale are then shown to have a quantum origin, involving threshold phenomena within a system of interacting ionization and HG channels, and to be sensitive to the bound state wave function's symmetry.