Attosecond transient absorption of argon atoms in the vacuum ultraviolet region: line energy shifts versus coherent population transfer
Attosecond transient absorption of argon atoms in the vacuum ultraviolet region: line energy shifts versus coherent population transfer
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DOI：
10.1088/1367-2630/18/1/013041
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发表时间：
2016-01-18
影响因子：
3.3
通讯作者：
Leone, Stephen R.
中科院分区：
文献类型：
--
作者：
Cao, Wei;Warrick, Erika R.;Leone, Stephen R.
利用阿秒瞬态吸收，研究了真空紫外区氩原子在外加电磁场作用下的偶极响应。一个孤立的阿秒真空紫外脉冲填充里德伯态躺在15 eV以上的氩基态。一个同步的几个周期的近红外（NIR）脉冲修改的振荡偶极氩脉冲，导致在真空紫外吸收光谱的改变。由于NIR脉冲相对于VUV脉冲被延迟，吸收轮廓中的多个特征同时出现，包括谱线加宽、边带结构、子周期快速调制和5-10 fs慢速调制。这些特征表明光-物质相互作用的两个一般过程共存：单个原子能级的能量移动和原子本征态之间的相干布居转移，揭示了相干叠加。一个直观的公式推导出一个统一的框架来处理这两种效果，允许一个识别和量化的两个过程中的一个单一的吸收光谱图。
Using attosecond transient absorption, the dipole response of an argon atom in the vacuum ultraviolet (VUV) region is studied when an external electromagnetic field is present. An isolated attosecond VUV pulse populates Rydberg states lying 15 eV above the argon ground state. A synchronized few-cycle near infrared (NIR) pulse modifies the oscillating dipoles of argon impulsively, leading to alterations in the VUV absorption spectra. As the NIR pulse is delayed with respect to the VUV pulse, multiple features in the absorption profile emerge simultaneously including line broadening, sideband structure, sub-cycle fast modulations, and 5-10 fs slow modulations. These features indicate the coexistence of two general processes of the light-matter interaction: the energy shift of individual atomic levels and coherent population transfer between atomic eigenstates, revealing coherent superpositions. An intuitive formula is derived to treat both effects in a unifying framework, allowing one to identify and quantify the two processes in a single absorption spectrogram.