Shock and Detonation Physics Group, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
J Phys Chem A. 2012 Oct 25;116(42):10301-9. doi: 10.1021/jp307464w. Epub 2012 Oct 15.
The response to ultrafast laser shock loading of nine liquids was monitored in an effort to reveal evidence of chemical changes occurring during the first 350 ps following the shock front. In an effort to compare molecular structures possessing a variety of common bonding patterns, data were acquired for the liquids: cyclohexane, cyclohexene, 1,3-cyclohexadiene, benzene, water, acetonitrile, acrylonitrile, tert-butylacetylene, and phenylacetylene. Transient absorption spectra were measured in the spectral region from 440 to 780 nm over shock stress states from 7 to 20 GPa. Ultrafast dynamic ellipsometry was used to measure the shock and particle velocity as well as the shocked refractive index. Significant transient absorption attributed to chemical reaction was observed for shocked phenylacetylene and acrylonitrile. Evidence of volume decreasing chemical reactions was also observed in the ultrafast dynamic ellipsometry data for phenylacetylene and acrylonitrile. The liquid 1,3-cyclohexadiene exhibited volume decreasing reaction in the ultrafast dynamic ellipsometry data but did not exhibit an increase in the transient absorption spectra. There was no evidence of chemical reaction in cyclohexane, cyclohexene, benzene, water, acetonitrile, or tert-butylacetylene in the first 350 ps, despite the application of shock stress that was in many cases well above the reaction threshold observed at microsecond time scales.
为了揭示在冲击波前沿后最初 350 ps 内发生的化学变化的证据，研究人员监测了九种液体对超快速激光冲击加载的响应。为了比较具有各种常见键合模式的分子结构，采集了以下液体的数据：环己烷、环己烯、1,3-环己二烯、苯、水、乙腈、丙烯腈、叔丁基乙炔和苯乙炔。在 440 至 780nm 的光谱区域内，测量了冲击压力状态为 7 至 20 GPa 的瞬态吸收光谱。超快动态椭圆偏振测量法用于测量冲击和粒子速度以及被冲击的折射率。在被冲击的苯乙炔和丙烯腈中观察到归因于化学反应的显著瞬态吸收。在苯乙炔和丙烯腈的超快动态椭圆偏振测量数据中也观察到体积减小的化学反应的证据。在超快动态椭圆偏振测量数据中，1,3-环己二烯显示出体积减小的反应，但在瞬态吸收光谱中没有增加。尽管在许多情况下应用的冲击压力远远高于微秒时间尺度上观察到的反应阈值，但在最初的 350 ps 内，环己烷、环己烯、苯、水、乙腈或叔丁基乙炔中均没有化学反应的证据。
