We perform velocity map imaging in the electrons generated from the ionization of ${\mathit{CH}}_{3}I$ molecules at 800 nm, in the intensity range 3.1 × 10¹³ $\mathrm{W}/{\mathrm{cm}}^2$ $⩽I⩽$6 × 10¹³ $\mathrm{W}/{\mathrm{cm}}^2$. The photoelectron spectra reveal a Freeman resonance at a peak intensity of $\approx$3.5 × 10¹³ $\mathrm{W}/{\mathrm{cm}}^2$. The photoelectron kinetic energy dependence on the laser intensity, as well as the observation of the 8-th photon channel closing offers absolute intensity calibration in our experiment, which allows for the accurate determination of the ponderomotive potential induced by the laser field and ultimately the determination of the Rydberg state involved in the Freeman resonance.

中文翻译：

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飞秒在碘甲烷飞秒电离中的Freeman共振的观察

我们对电子的电离产生的电子进行速度图成像 ${\mathit{CH}}_3\mathrm{一世}$分子在800 nm处的强度范围为3.1×10 ¹³ $\mathrm{w\; ^}/{\mathrm{厘米}}^2$ $⩽\mathrm{一世}⩽$6×10 ¹³ $\mathrm{w\; ^}/{\mathrm{厘米}}^2$。光电子能谱显示峰强度为的Freeman共振。$\approx$3.5×10 ¹³ $\mathrm{w\; ^}/{\mathrm{厘米}}^2$。光电子动能对激光强度的依赖性以及对第8个光子通道闭合的观察在我们的实验中提供了绝对强度校准，从而可以准确确定由激光场感应的磁势，并最终确定里德堡州的弗里曼共鸣。