Wavelength dependence of high-harmonic yield in stretched molecules

Abstract

We study the wavelength dependence of harmonic yield in stretched molecules. It is found that when the laser field is perpendicular to the molecular axis, the harmonic yield has a slow scaling λ-4.27 as the increase of the laser wavelength for the stretched molecule H2+ with the internuclear distance of 7a.u. compared with λ-5.11 for H2+ at the equilibrium position. Further analysis shows that the narrower width of the initial wave-function in the momentum space is in charge of the slow wavelength scaling of the stretched molecule since it can make the wave-function spreading less during propagation. Moreover, a higher enhancement and a better wavelength scaling of harmonic yield both can be achieved at the optimal internuclear distance of 7a.u.