Aarhus Universitets segl

Frederik Doktor Simonsen

As a Postdoc under InterCat I am studying atom functionalization of hydrocarbon chains within an astrochemical context, as well as sub-monolayer ice growth on interstellar dust analogues at temperatures < 10 K.

My research carrier started at Aarhus University, Denmark, where I completed both my Bachelors (BSc), Masters (MSc) and PhD in Physics with a focus on experimental surface science and astrochemistry. A 2-year Postdoc position followed at the Center for Interstellar Catalysis (InterCat), before moving to Spain for 1 year to work with the ESISNA group of José Ángel Martín Gago at ICMM-CSIC, Madrid.

In Madrid I mainly focused on studying meteoritic material, from ALLENDE and Almahata Sitta, with LT-STM and AFM to determine molecular structures which may not be resolved using mass spectroscopy data. I also spend time with the STARDUST setup to examine interstellar dust grain analogues formed under close to realistic interstellar conditions.

My early studies focused mainly on polycyclic aromatic hydrocarbons (PAHs) and their role in interstellar astrochemistry. PAHs are thought to be abundant in interstellar space, constituting upwards of 10-20% of all carbon in the ISM, and carriers of the aromatic infrared (IR) bands (AIBs). PAHs are stable aromatic molecules that may survive under harsh conditions of the ISM, e.g. in photodissociation regions (PDRs), where ultra violet (UV) radiation fields govern the chemistry and temperatures reach from hundreds to thousands of Kelvin.

I have explored how PAHs:

  • Interact with graphitic surfaces
  • Catalyse small molecule formation through hydrogenation and oxidation processes
  • Influence the AIBs when superhydrogenated
  • Fragment in particular patterns, evaporating molecular hydrogen or small hydrocarbons

In more recent studies I have shifted my focus to colder regions of the interstellar medium, where temperatures reach 10 K or less. Specifically, I have investigated amorphous solid water (ASW) ice growth on graphite, an interstellar dust grain analogue. Interstellar dust grains will start to build up layers of ice, of which the main constituent is water formed on the grain itself, when temperature drop in the ISM, e.g. inside giant molecular clouds (GMCs). Other chemical process take place on and in the ice forming interstellar complex organic molecules (COMs) and possibly even the molecular building blocks of life, such as sugars, amino acids, fats and DNA bases. Hence, it is important to understand the ice structure and its influence on these reactions to map the chemistry and catalytic effect of interstellar dust grains.

I have explored how water ices:

  • Diffuse, grow and form clusters in the sub-monolayer regime on pristine graphite
  • Diffuse, grow and form clusters in the sub-monolayer regime on oxygen functionalized graphite
  • Form fractal or dense 2D structures at various surface temperatures
  • Exhibit near diffusion limited aggregation (DLA) at low surface temperatures

During my research I have worked with several experimental techniques:

  • Temperature programmed desorption (TPD)
  • Low-temperature scanning tunneling microscopy (LT-STM)
  • Atomic Force Microscopy (AFM)
  • IR action gas-phase spectroscopy, using free electron lasers (FELs), collision induced dissociation (CID) and IR multiphoton dissociation (IRMPD)
  • X-ray photoelectron spectroscopy (XPS)
  • Techniques used to lesser degree are, low energy electron diffraction (LEED) and Auger electron spectroscopy (AES)
  • Kinetic Monte Carlo (KMC) simulations

I’m an open and outreaching person who enjoys traveling the world and participate in international collaborations or conferences, where I will happily present my research and hope to meet and engage with new people as well as old collaborators. Nevertheless, I find it just as intriguing to sit in the lab for hours on end, revealing the newest concepts within my field of research.

Outside of work I enjoy a good craft beer, motorcycling (not in tandem with the former interest I might add ;)), friends and family, PC programming/gaming, traveling and in general trying new things.

Postdoctoral fellow

frederik_doktor@phys.au.dk

1520-326 Ny Munkegade 120

DK-8000 Aarhus C