Astrophysical Implications of PAH Clusters

Biswas, Ayanava (2022) Astrophysical Implications of PAH Clusters. Masters thesis, Indian Institute of Science Education and Research Kolkata.

Text (MS dissertation of Ayanava Biswas (17MS119)) 17MS119_Thesis_file.pdf - Submitted Version Restricted to Repository staff only Download (3MB)

Abstract

In this project we will mainly deal with properties of Polycyclic Aromatic Hydrocarbon (PAHs) clusters. They forms clusters by non-covalent bonds and binds together by mainly Van Der Waals attractive force. There is also repulsive force from π electron cloud surrounded by it. Apart from that they get additional stability by two other short range non covalent bond known as π − π stacking and CH − π interaction. Here possibility, geometry, other physical properties like binding energy, theoretical IR spectra are are explored computationally. This PAHs also have high relevance in astrochemistry. They are believed to be the main source of mid-IR features of various astrophysical objects. Hence a lot of effort has been given to have a huge database on IR spectra of PAHs to simulate those mid-IR features. This project also aims to contribute in that by investigating cluster of PAHs and also N-substituted PAHs (aka PANHs). Here we will show that parallel oriented (π − π stacking) cluster formation results in red-shifting and T orientation (CH −π interaction) results in blue-shifting. We will also show that for cyclic and larger PAHs π − π interaction is more relevant and so their clusters are parallel and displaced. At the end we will try to show consistency between our computational work and previous experimental work.

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