Surface science investigations into the interstellar molecule propylene oxide Kerry Jones, Wendy Brown, Jack Fulker School of Life Sciences, University of Sussex, UK Propylene oxide, CH 3 CHCH 2 O, has recently been detected in the gas-phase in the interstellar medium (ISM). Propylene oxide is an important molecule as it is chiral, and it is also a structural isomer of acetone, another important interstellar molecule. Propylene oxide is classified as a complex organic molecule (COM). COMs are an important family of molecules in astrochemistry as they are considered to be pre-biotic. Propylene oxide is a good candidate to exist in the solid phase, as similar COMs have been detected in ices which accrete onto dust grains in colder regions of the ISM. The surface chemistry occurring in these molecular ices accounts for the enhanced abundances of COMs in the gas phase within star-forming regions of the ISM. With this in mind, we have undertaken a detailed surface science study of the adsorption and desorption of propylene oxide and water containing ices, adsorbed on a model dust grain surface. Surface science experiments including temperature programmed desorption (TPD) and reflection absorption infrared spectroscopy (RAIRS) have been performed on model ices grown on a highly oriented pyrolytic graphite (HOPG) substrate surface. Using an ultra-high vacuum chamber which allows cooling of the substrate to 30 K, we were able to mimic the low temperature and pressure conditions of the ISM. Ice configurations that were investigated include pure propylene oxide and propylene oxide as a component of layered and mixed molecular ices with water. RAIRS and TPD allowed the characterisation of the adsorption and thermal desorption behaviour of these ices by probing the structural changes of the ices during annealing and identifying any molecular interactions that occur between the ices. Propylene oxide desorbs from the HOPG surface over a temperature range from 120-140 K dependent on the ice configuration. Multilayer, monolayer, and volcano desorption peaks are observed in TPD spectra. This research is timely due to the launch of the James Webb Space Telescope and the observation of the first data showing the presence of COMs in a number of different astrophysical environments. References
1. D. J. Burke and W. A. Brown, Phys. Chem. Chem. Phys., 2010, 12 , 5947–5969. 2. R.L. Hudson, M. J. Loeffler and K. M. Yocum, Astrophys. J., 2017, 835 , 225.
P26
© The Author(s), 2023
Made with FlippingBook Learn more on our blog