Department of Chemistry, University of Georgia, Athens, Georgia 30602, USA.
J Chem Phys. 2013 May 7;138(17):174302. doi: 10.1063/1.4802767.
The vinyl radical has been trapped in (4)He nanodroplets and probed with infrared laser spectroscopy in the CH stretch region between 2850 and 3200 cm(-1). The assigned band origins for the CH2 symmetric (ν3), CH2 antisymmetric (ν2), and lone α-CH stretch (ν1) vibrations are in good agreement with previously reported full-dimensional vibrational configuration interaction computations [A. R. Sharma, B. J. Braams, S. Carter, B. C. Shepler, and J. M. Bowman, J. Chem. Phys. 130, 174301 (2009)]. For all three bands, a-type and b-type transitions are observed from the lowest symmetry allowed roconvibrational state of each nuclear spin isomer, which allows for a determination of the tunneling splittings in both the ground and excited vibrational levels. Comparisons to gas phase millimeter-wave rotation-tunneling [K. Tanaka, M. Toshimitsu, K. Harada, and T. Tanaka, J. Chem. Phys. 120, 3604-3618 (2004)] and high-resolution jet-cooled infrared spectra [F. Dong, M. Roberts, and D. J. Nesbitt, J. Chem. Phys. 128, 044305 (2008)] reveal that the He solvent effect is to reduce the ground and ν3 excited state tunneling splittings by ≈20%. This solvent-induced modification of the tunneling dynamics can be reasonably accounted for by assuming either a ≈2.5% increase in the effective barrier height along the tunneling coordinate or a ≈5% increase in the effective reduced mass of the tunneling particles.
乙烯基自由基已被捕获在 (4)He 纳米液滴中，并在 2850 至 3200cm(-1) 的 CH 伸缩区域用红外激光光谱进行探测。CH2 对称（ν3）、CH2 反对称（ν2）和孤立 α-CH 伸缩（ν1）振动的指定带起源与先前报道的全维振动构象相互作用计算[A. R. Sharma、B. J. Braams、S. Carter、B. C. Shepler 和 J. M. Bowman，J. Chem. Phys. 130, 174301 (2009)]吻合良好。对于所有三个带，从每个核自旋异构体的最低对称允许 roconvibrational 态观察到 a 型和 b 型跃迁，这允许确定基态和激发振动能级中的隧道分裂。与气相毫米波旋转隧道[K. Tanaka、M. Toshimitsu、K. Harada 和 T. Tanaka，J. Chem. Phys. 120, 3604-3618 (2004)]和高分辨率喷射冷却红外光谱[F. Dong、M. Roberts 和 D. J. Nesbitt，J. Chem. Phys. 128, 044305 (2008)]的比较表明，He 溶剂效应将基态和 ν3 激发态隧道分裂降低约 20%。通过假设隧道坐标沿隧道坐标的有效势垒高度增加约 2.5%或隧道粒子的有效约 5%的有效约 5%，可以合理地解释这种隧道动力学的溶剂诱导修饰。
