Amorphous 1-propanol interstellar ice beyond its melting point

Ramachandran, R and Hazarika, A and Gupta, S and Nag, S and Meka, JK and Thakur, TS and Yashonath, S and Vishwakarma, G and Chou, S-L and Wu, Y-J and Janardhan, P and Rajasekhar, BN and Bhardwaj, A and Mason, NJ and Sivaraman, B and Maiti, PK (2024) Amorphous 1-propanol interstellar ice beyond its melting point. In: Monthly Notices of the Royal Astronomical Society, 530 (1). pp. 1027-1034.

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Abstract

The recent discovery of 1-propanol (CH3CH2CH2OH) in the interstellar medium (ISM) is of tremendous interest since fatty alcohols have been proposed as constituents of proto-cell membranes. Motivated by this discovery, we present the laboratory mid-infrared (MIR) and vacuum ultraviolet (VUV) absorption spectra of 1-propanol ice under astrochemical conditions, mimicking an icy mantle on cold dust in the ISM. Both MIR and VUV spectra were recorded at ultrahigh vacuum of �10-9 mbar and at temperatures ranging from 10 K to sublimation. The morphology of the 1-propanol ice deposited at 10 K was amorphous. By warming the ice to temperatures of 140 K and above, with subsequent recording of IR spectra, we observe complete sublimation of 1-propanol molecules from the substrate around 170 K. No amorphous-to-crystalline phase change was observed upon warming to higher temperatures. Additionally, we observe the IR and VUV signatures of 1-propanol ice on the substrate well beyond its melting point (147 K). To the best of our knowledge, this is the first reported observation of a molecular ice staying well beyond its melting point under such conditions. This result shows that the morphology of icy mantles on ISM cold dust grains is more complex than previously thought. Our atomistic molecular dynamics simulations capture the experimental trends and shed light on the microscopic origin of this unusual phase behaviour of 1-propanol. © 2024 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society.

Item Type:	Journal Article
Publication:	Monthly Notices of the Royal Astronomical Society
Publisher:	Oxford University Press
Additional Information:	The copyright for this article belongs to authors.
Keywords:	Alcohols; Cytology; Dust; Melting point; Molecular dynamics; Molecules; Morphology; Sublimation, 1-propanol; Astrochemistry; Condition; Infrared: general; Interstellar medias; Interstellar medium: molecules; Methods:statistical; Midinfrared; Molecular data; Software simulation, Ice
Department/Centre:	Division of Chemical Sciences > Solid State & Structural Chemistry Unit Division of Physical & Mathematical Sciences > Physics
Date Deposited:	09 Jul 2024 13:03
Last Modified:	09 Jul 2024 13:03
URI:	http://eprints.iisc.ac.in/id/eprint/84765

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