Astrophysical Chemistry

Dr. D. Field and Dr. M.Gray

The projects offered are theoretical and mainly computer-based projects. They involve investigating how to interpret astronomical data using chemical knowledge. A number of the aspects of the work are closely related to the 3rd year Chemistry course work, for example, statistical mechanics and molecular spectroscopy. These projects also give students experience in manipulating large computer codes and in data handling, using large mainframe computers, such as the Bristol IBM or the Cray YMP at the Rutherford-Appleton Laboratory.

In the last two decades, nearly one hundred different molecular species have been identified in the interstellar medium. These range from the simplest, such as H2, to quite complex chain molecules such as C6H or a number of cyano-polyynes. Searches for bio-molecules, such as amino acids, have so far proved negative, but success could be around the corner. The rich mixture of molecules found implies a rich chemistry, which is being intensively investigated in many laboratories and observatories throughout the world. In order to understand this chemistry, we have to know the physical conditions of their environment, that is the temperature and number density of the molecular constituents and of the hydrogen molecules, which make up the great bulk of the material. The calculation of these physical conditions constitutes a major part of the interpretation of astronomical spectra.

The projects offered are concerned with this field of research. They span a wide range of physical chemistry, involving emission and absorption of light, molecular energy transferring collisions, spectroscopic properties of radicals, surface properties of dust particles etc.. The content of the project is flexible and allows students to follow their interests, which develop during an introductory learning period. Projects for the coming year are likely to fall into one of the categories listed below.

  1. Understanding the presence, in regions where star form, of very intense microwave laser-like radiation ("celestial masers") involving OH, H2O or SiO.
  2. Investigating how whole galaxies emit maser radiation, the so-called "megamasers". There are about 50 such galaxies known.
  3. Investigating the origin of emission from H2O molecules, recently detected in a very distant galaxy, at an epoch when the universe was les than a quarter of its present age.
  4. Investigating the mechanism by which populations inversions are formed in OH molecules, leading to maser action.
A good starting reference is J.Chem.Soc. Faraday Trans. (1993) 89, 2231-2237 for more detailed information on the character of the work involved.

Students enter a group consisting of Malcolm Gray, David Field, Jeremy Yates (Post-Doctoral Research Assistant) in Chemistry and Robin Walker, Rodney Hillier, Michael Masheder and Richard Oliver (Post-Graduate Student) in Physics. We meet regularly as a group each week.