Possible Formation of Metastable PAH Dimers upon Pickup by Helium Droplets

详细信息    查看全文

• 作者：F. Calvo ; E. Yurtsever ; Ö. Birer
• 刊名：Journal of Physical Chemistry A
• 出版年：2016
• 出版时间：March 17, 2016
• 年：2016
• 卷：120
• 期：10
• 页码：1727-1736
• 全文大小：552K
• ISSN：1520-5215

文摘

Using path-integral molecular dynamics simulations and two quantum-mechanical-based force fields, we have investigated the conformational stability of dimers of a polycyclic aromatic hydrocarbon, perylene (C₂₀H₁₂), produced under typical experimental conditions of successive pick-up under helium nanodroplet environment. The most stable configurations are found to be of the stacked form with different relative orientations of the main molecular axes, perpendicular or T-shaped dimers being energetically much disfavored; however, in the presence of helium our simulations suggest that the time for rearrangement and π-stacking may be rather long and exceed hundreds of picoseconds. In addition, highly metastable dimers that are stacked but with a helium monolayer sandwiched between the two molecules are also found as likely products upon successive pickup. This stabilization occurs owing to the stronger localization of the helium atoms facing the aromatic rings, which is further enhanced in the dimer. The implications of the present results are discussed in the perspective of possible identification by spectroscopic methods.