Identification of a unique VUV photoabsorption band of carbonic acid for its identification in radiation and thermally processed water-carbon dioxide ices

S Pavithraa; J-I Lo; B-M Cheng; B N Raja Sekhar; N J Mason; B Sivaraman

doi:10.1016/j.saa.2019.02.037

Identification of a unique VUV photoabsorption band of carbonic acid for its identification in radiation and thermally processed water-carbon dioxide ices

Spectrochim Acta A Mol Biomol Spectrosc. 2019 May 15:215:130-132. doi: 10.1016/j.saa.2019.02.037. Epub 2019 Feb 17.

Authors

S Pavithraa¹, J-I Lo², B-M Cheng², B N Raja Sekhar³, N J Mason⁴, B Sivaraman⁵

Affiliations

¹ Atomic Molecular and Optical Physics Division, Physical Research Laboratory, Ahmedabad, India.
² National Synchrotron Radiation Research Center, Hsinchu, Taiwan.
³ B-1, Indus-1, Atomic and molecular Physics division, Bhabha Atomic Research Centre at RRCAT, Indore, India.
⁴ School of Physical Sciences, University of Kent, Canterbury, United Kingdom.
⁵ Atomic Molecular and Optical Physics Division, Physical Research Laboratory, Ahmedabad, India. Electronic address: bhala@prl.res.in.

PMID: 30825863
DOI: 10.1016/j.saa.2019.02.037

Abstract

Carbonic acid was synthesized within an ice containing water and carbon dioxide by irradiation of ~9 eV photons. Vacuum UltraViolet (VUV)/UltraViolet (UV) photoabsorption spectra of the irradiated ice revealed absorption features from carbon dioxide, ozone, water, carbon monoxide and oxygen in addition to a band peaking at ~200 nm which is identified to be characteristic of carbonic acid. After thermal processing of the irradiated ice leading to desorption of the lower volatile ices, a pure carbonic acid spectrum is identified starting from 170 K until sublimation above 230 K. Therefore the ~200 nm band in the VUV region corresponding to carbonic acid is proposed to be a unique identifier in mixed ices, rich in water and carbon dioxide typically encountered on planetary and satellite surfaces.

Keywords: Astrochemistry; Laboratory; Methods; Solid state; Spectroscopic; Techniques.