Wavelength Scaling of High-Harmonic Yield: Threshold Phenomena and Bound State Symmetry Dependence

Abstract

Describing harmonic generation (HG) in terms of a system's complex quasienergy, the harmonic power ${P}_{\ensuremath{\Delta}E}(\ensuremath{\lambda})$ (over a fixed interval, $\ensuremath{\Delta}E$, of harmonic energies) is shown to reproduce the wavelength scaling predicted recently by two groups of authors based on solutions of the time-dependent Schr\"odinger equation: ${P}_{\ensuremath{\Delta}E}(\ensuremath{\lambda})\ensuremath{\sim}{\ensuremath{\lambda}}^{\ensuremath{-}x}$, where $x\ensuremath{\approx}5--6$. Oscillations of ${P}_{\ensuremath{\Delta}E}(\ensuremath{\lambda})$ on a fine $\ensuremath{\lambda}$ 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.