Ou Jen-Hao, Hait Diptarka, Rupprecht Patrick, Beetar John E, Martínez Todd J, Leone Stephen R
Department of Chemistry, University of California, Berkeley, California 94720, United States.
Department of Chemistry and The PULSE Institute, Stanford University, Stanford, California 94305, United States.
J Phys Chem A. 2024 Oct 24;128(42):9208-9217. doi: 10.1021/acs.jpca.4c05210. Epub 2024 Oct 14.
A coherent vibrational wavepacket is launched and manipulated in the symmetric stretch (a) mode of CBr, by impulsive stimulated Raman scattering (ISRS) from nonresonant 400 nm laser pump pulses with various peak intensities on the order of tens of 10 W/cm. Extreme ultraviolet (XUV) attosecond transient absorption spectroscopy (ATAS) records the wavepacket dynamics as temporal oscillations in XUV absorption energy at the bromine M 3d edges around 70 eV. The results are augmented by nuclear time-dependent Schrödinger equation simulations. Slopes of the (Br 3d)10a* core-excited state potential energy surface (PES) along the a mode are calculated to be -9.4 eV/Å from restricted open-shell Kohn-Sham calculations. Using analytical relations derived for the small-displacement limit and the calculated slopes of the core-excited state PES, a deeper insight into the vibrational dynamics is obtained by retrieving the experimental excursion amplitude of the vibrational wavepacket and the amount of population transferred to the vibrational first-excited state as a function of pump-pulse peak intensity. Experimentally, the results show that XUV ATAS is capable of resolving oscillations in the XUV absorption energy on the order of a few to tens of meV with tens of femtosecond time precision. This corresponds to change in C-Br bond length on the order of 10 to 10 Å. The results and the analytic relationships offer a clear physical picture, on multiple levels of understanding, of how the pump-pulse peak intensity controls the vibrational dynamics launched by nonresonant ISRS in the small-displacement limit.
通过对具有数十10 W/cm量级不同峰值强度的非共振400 nm激光泵浦脉冲进行脉冲受激拉曼散射（ISRS），在CBr的对称拉伸（a）模式下产生并操控一个相干振动波包。极紫外（XUV）阿秒瞬态吸收光谱（ATAS）记录了波包动力学，表现为在约70 eV的溴M 3d边缘处XUV吸收能量的时间振荡。核含时薛定谔方程模拟增强了这些结果。通过受限开壳层Kohn-Sham计算，（Br 3d）10a* 芯激发态势能面（PES）沿a模式的斜率计算为-9.4 eV/Å。利用针对小位移极限推导的解析关系以及芯激发态PES的计算斜率，通过获取振动波包的实验偏移幅度和转移到振动第一激发态的布居数量作为泵浦脉冲峰值强度的函数，对振动动力学有了更深入的了解。实验结果表明，XUV ATAS能够以数十飞秒的时间精度分辨XUV吸收能量中几到几十meV量级的振荡。这对应于C-Br键长10到10 Å量级的变化。这些结果和解析关系在多个理解层面上清晰地展现了泵浦脉冲峰值强度如何在小位移极限下控制由非共振ISRS引发的振动动力学。
