(G)astrochemistry

January 5, 2019 by anon


My research work is in an interesting and highly interdisciplinary field called Astrochemistry. Alexander Dalgarno, a pioneer in the field describes it as

“the study of the formation, destruction and excitation of molecules in astronomical environments and their influence on the structure, dynamics and evolution of astronomical objects”

The field itself is vast and includes theoreticians, astronomers and experimental physicists. I do experimental physics and my work comes under what is called ‘laboratory astrophysics’. I can’t describe it better than what is stated on https://www.astro.uni-jena.de/Laboratory/Speclab/labor.html

“Laboratory astrophysics is one of the youngest branches of astrophysics. Its name was coined about 30 years ago in order to denote the investigation of the solid phases in astrophysical environments by laboratory simulation experiments. Today, this new field has developed to a kind of galactic material science.

Main topics of this field are:

  • the absorption and emission spectra of dust, molecules, ions, and radicals
  • the “mineralogy” of dust particles and its relation to their optical properties
  • reactions of molecules and ions in the gas phase as well as on grain surfaces
  • interaction of dust grains with UV and ion radiation as well as heat, leading to structural changes
  • properties of interplanetary dust, cometary and meteoritic grains
  • aggregation, growth and destruction of dust grains leading to planet formation”

    The Ultrahigh Vacuum Chamber I conduct my experiments in. But the best vacuum we can achieve is still not as good as that in the interstellar medium.

I study reactions of a family of molecules called polycyclic aromatic hydrocarbons, PAHs for short, on grain surfaces using surface science techniques. The scanning tunneling microscope is one of them and I use it to ‘image’ these molecules on a surface. To make sure that the molecules don’t move around too much when I’m imaging them, I cool the molecules with liquid nitrogen.

Liquid nitrogen has a boiling point of -195.79 °C at atmospheric pressure so that as soon as you pour it out it boils and evaporates by taking away heat from whichever object it comes into contact with thereby cooling it rapidly. Liquid nitrogen is usually stored in a vacuum flask or Dewar and kept at a temperature of -196.15 °C so that it boils slowly. This means that the Dewar will be empty a few days after filling it.

The lemon sorbet with rosemary garnish ready to be devoured on a hot day

I had some problems with the STM so I couldn’t use it for a few days. Instead of wasting the liquid nitrogen that I had already brought from the workshop, a colleague suggested that we use it to make ice cream! While pitching ideas for the flavour, we concluded that it would be easier to make sorbet instead considering the limited kitchenware we had. After a long discussion over lunch break, we decided to make lemon sorbet with rosemary garnish the next day.

It’s really easy to make sorbet! Take sugar syrup, a flavoured concentrate of your choice in a large bowl and then pour liquid nitrogen in and whisk away with all the strength you can muster. We used Jamie Oliver’s recipe. We weren’t too sure how much liquid nitrogen to add at first so we ended up pouring too little and the mixture was only getting cold but not crystalline. Gradually we got the amount of liquid nitrogen right and after taking turns to whisk vigorously, we finally had a sorbet! I’m not sure if it actually tasted good or we were just too excited to give it a thought. You can find the recipe we followed here: https://www.jamieoliver.com/recipes/fruit-recipes/lemon-sorbet/

 

Step by step sequence of making the raspberry sorbet

We made raspberry sorbet the next week. The plan is to keep it going, a new flavour every week. Hawthorne, coffee… leave a comment if you have an interesting flavour suggestion.

Be careful with liquid nitrogen! Read this document before you use liquid nitrogen. https://www.ars.usda.gov/ARSUserFiles/80000000/SHE/LN%20safety.docx


Guest post written by Rijutha Jaganathan

Rijutha Jaganathan is a PhD student at Aarhus University, Denmark. She is an early stage researcher under the Marie-Sklodowska Curie ITN, funded under Horizon 2020 – ‘’EUROPAH’’. She combines her passion for astronomy with experimental surface science techniques like Scanning Tunneling Microscopy and X-ray Photoelectron Spectroscopy to study and understand the catalytic properties of Polycyclic Aromatic Hydrocarbons (PAHs) in the interstellar medium. She is equally passionate about art, architecture and history. When she is not in the lab, she is either engrossed in a book with a mug of coffee or is exploring a city by foot with a camera in hand.

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