Electronic Structure of Liquid Alkanes: A Representative Case of Liquid Hexanes and Cyclohexane Studied Using Polarization-Dependent Two-Photon Absorption Spectroscopy,The Journal of Physical Chemistry A

当前位置： X-MOL 学术 › J. Phys. Chem. A › 论文详情

Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)

Electronic Structure of Liquid Alkanes: A Representative Case of Liquid Hexanes and Cyclohexane Studied Using Polarization-Dependent Two-Photon Absorption Spectroscopy
The Journal of Physical Chemistry A ( IF 2.7 ) Pub Date : 2021-09-03 , DOI: 10.1021/acs.jpca.1c06230
Dhritiman Bhattacharyya ₁ , Yuyuan Zhang ₁ , Christopher G Elles ₁ , Stephen E Bradforth ₁

Affiliation

Two-photon absorption (2PA) spectra of liquid cyclohexane and hexanes are reported for the energy range 6.4–8.5 eV (177–145 nm), providing detailed information about their electronic structures in bulk liquid. Using a broadband pump–probe fashion, we measured the continuous 2PA spectra by simultaneous absorption of a 266 nm (4.6 eV) pump photon and one UV–vis probe photon from the white-light continuum (1.8–3.9 eV). Theoretical one-photon absorption (1PA) and 2PA cross sections of isolated gas phase molecules are computed by the equation of motion coupled-cluster method with single and double substitutions (EOM-CCSD) to substantiate the assignment of the experimental spectra, and the natural transition orbital (NTO) analysis provides visualization of the participating orbitals in a transition. Our analysis suggests that upon solvation transitions at the lowest excitation energy involving promotion of electron to the 3s Rydberg orbitals are blue-shifted (∼0.55 eV for cyclohexane and ∼0.18 eV for hexanes) to a greater extent as compared to those involving other Rydberg orbitals, which is similar to the behavior observed for water and alcohols. All other transitions experience negligible (cyclohexane) or minor red-shift by ∼0.15-0.2 eV (hexane) upon solvation. In both alkanes, the spectra are entirely dominated by Rydberg transitions: the most intense bands in 1PA and 2PA spectra are due to the excitation of electrons to the Rydberg “p” and “d” type orbitals, respectively, although one transition terminating in the 3s Rydberg has significant 2PA strength. This work demonstrates that the gas phase electronic transition properties in alkanes are not significantly altered upon solvation. In addition, electronic structure calculations using an isolated-molecule framework appear to provide a reasonable starting point for a semiquantitative picture for spectral assignment and also to analyze the solvatochromic shifts for liquid phase absorption spectra.

中文翻译：

液体烷烃的电子结构：使用偏振相关双光子吸收光谱研究液体己烷和环己烷的代表性案例

据报道，液体环己烷和己烷的双光子吸收 (2PA) 光谱能量范围为 6.4-8.5 eV（177-145 nm），提供了有关它们在散装液体中的电子结构的详细信息。使用宽带泵浦-探针方式，我们通过同时吸收来自白光连续谱 (1.8-3.9 eV) 的 266 nm (4.6 eV) 泵浦光子和一个 UV-vis 探测光子来测量连续 2PA 光谱。孤立的气相分子的理论单光子吸收 (1PA) 和 2PA 横截面是通过运动方程与单取代和双取代 (EOM-CCSD) 计算的，以证实实验光谱的分配，以及自然过渡轨道 (NTO) 分析提供了过渡中参与轨道的可视化。我们的分析表明，与涉及其他里德堡轨道的那些相比，在涉及将电子提升到 3s 里德堡轨道的最低激发能量下的溶剂化跃迁蓝移程度更大（环己烷约为 0.55 eV，己烷约为 0.18 eV），这类似于对水和醇观察到的行为。所有其他跃迁在溶剂化时都经历了可忽略不计的（环己烷）或轻微的红移~0.15-0.2 eV（己烷）。在这两种烷烃中，光谱完全由里德堡跃迁主导：1PA 和 2PA 光谱中最强烈的带是由于电子分别激发到里德堡“p”和“d”型轨道，尽管一个跃迁终止于3s Rydberg 具有显着的 2PA 强度。这项工作表明烷烃中的气相电子跃迁特性在溶剂化后没有显着改变。此外，使用孤立分子框架的电子结构计算似乎为光谱分配的半定量图片提供了合理的起点，也为分析液相吸收光谱的溶剂化变色位移提供了合理的起点。

更新日期：2021-09-16

点击分享查看原文

点击收藏

阅读更多本刊最新论文