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

• Published in: Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy
• Main Authors: Pavithraa, S, Lo, J.-I., Cheng, B.-M., Sekhar, B.N. Raja, Mason, Nigel, Sivaraman, B.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Elsevier 2019
• Subjects: Carbonic acid
• Online Access: https://kar.kent.ac.uk/73019/; https://doi.org/10.1016/j.saa.2019.02.037

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.