Residue from vacuum ultraviolet irradiation of benzene ices: Insights into the physical structure of astrophysical dust

K K Rahul; E Shivakarthik; J K Meka; A Das; V Chandrasekaran; B N Rajasekhar; J-I Lo; B-M Cheng; P Janardhan; A Bhardwaj; N J Mason; B Sivaraman

doi:10.1016/j.saa.2019.117797

Residue from vacuum ultraviolet irradiation of benzene ices: Insights into the physical structure of astrophysical dust

Spectrochim Acta A Mol Biomol Spectrosc. 2020 Apr 15:231:117797. doi: 10.1016/j.saa.2019.117797. Epub 2019 Nov 13.

Authors

K K Rahul¹, E Shivakarthik¹, J K Meka¹, A Das², V Chandrasekaran³, B N Rajasekhar⁴, J-I Lo⁵, B-M Cheng⁵, P Janardhan¹, A Bhardwaj¹, N J Mason⁶, B Sivaraman⁷

Affiliations

¹ Physical Research Laboratory, Ahmedabad, India.
² Indian Centre for Space Physics, Kolkata, India.
³ Vellore Institute of Technology, Vellore, India.
⁴ Atomic and Molecular Physics Division, Bhabha Atomic Research Centre, Mumbai, India.
⁵ National Synchrotron Radiation Research Center, Hsinchu, Taiwan.
⁶ School of Physical Sciences, University of Kent, Canterbury, Kent CT2, UK.
⁷ Physical Research Laboratory, Ahmedabad, India. Electronic address: bhala@prl.res.in.

PMID: 31837964
DOI: 10.1016/j.saa.2019.117797

Abstract

We have irradiated benzene ices deposited at 4 K on a cold, interstellar dust analog with vacuum ultraviolet (9 eV) irradiation for periods lasting from several hours to nearly a day, after which the irradiated ice was warmed to room temperature. Vacuum ultraviolet photoabsorption spectra of the aromatic residue left at room temperature were recorded and showed the synthesis of benzene derivatives. The residue was also imaged using an electron microscope and revealed crystals of various sizes and shapes. The result of our experiments suggests such geometrically shaped dust particles may be a key component of interstellar dust.

Keywords: Aromatic residue; Astrophysical dust; Benzene ice; Interstellar medium; Vacuum ultraviolet spectroscopy.