Abstract Details
| Name: Rashmi Singh Affiliation: DDU Gorakhpur University,Gorakhpur (UP)-273009 Conference ID: ASI2018_1730 Title : Vibrational transitions in phenyl and vinyl derivatives of polycyclic aromatic hydrocarbons in relation to astrophysical infrared bands Authors and Co-Authors : Anju Maurya and Shantanu Rastogi DDU Gorakhpur University,Gorakhpur(UP)-273009 Abstract Type : Poster Abstract Category : Stars,ISM and the Galaxy Abstract : The astrophysical observations of mid-infrared emission features at 3.3, 6.2, 7.7, 8.6, 11.2 and 12.7 µm (3030, 1610, 1300, 1160, 890 and 790 cm-1) are attributed to vibrational transitions in polycyclic aromatic hydrocarbon (PAH) molecules. These aromatic infrared bands (AIBs) are ubiquitously observed in a variety of astrophysical objects from star forming regions to late type stars and even in external galaxies. The variation in the profile of these emission features correlates with object type indicating different PAH types and populations in different astrophysical environments. The composite emission spectra from a collection of PAHs show uncertainty in matching the 6.2 µm feature AIB, assigned to aromatic C-C stretching vibration. This suggests that only plain PAHs are not sufficient for emission modeling and other forms of PAHs need to be considered, including derivatives, in emission models. The proposed chemical pathway of the formation of PAH molecules in circumstellar environment shows the presence of vinyl and phenyl derivatives of PAHs as intermediate products. The study of these derivatives may improve the proposed emission models and can give a better insight for the observed AIBs. In the present work, we employ density functional method at DFT/4-31G level of theory to compute the infrared vibrational spectra of PAH molecules with substitution of side groups including Vinyl and Phenyl. The aim is to study their suitability, in terms of intensity, peak position and profile, for explaining the astrophysical AIBs. Theoretical IR spectra of Vinyl and Phenyl Anthracene produce almost similar features but Vinyl PAHs show some improvement towards observational features as compared to phenyl PAHs. |