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${\lambda }^{-4.27}$ as the increase of the laser wavelength for the stretched molecule ${\text{H}}_2^{+}$ with the internuclear distance of 7 a.u. compared with λ^-5.11${\lambda }^{-5.11}$ for ${\text{H}}_2^{+}$ 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 7 a.u..

中文翻译：

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拉伸分子中高谐波产量的波长依赖性

我们研究了拉伸分子中谐波产量的波长依赖性。发现当激光场垂直于分子轴时，谐波产量具有缓慢的缩放λ- ^4.27${\lambda }^{--4.27}$ 随着被拉伸分子的激光波长的增加 ${\text{H}}_{\mathrm{2个}}^{+}$核间距为7 au与λ- ^5.11比较${\lambda }^{--5.11}$ 为了 ${\text{H}}_{\mathrm{2个}}^{+}$在平衡位置。进一步的分析表明，动量空间中初始波函数的较窄宽度负责拉伸分子的慢波长缩放，因为它可以使波函数在传播过程中扩展较少。而且，在7 au的最佳核间距下，都可以实现更高的增强和更好的谐波产量的波长定标。