A model for mysterious molecular hydrogen reactions

Curtin University alumnus Mark Zammit has led the development of a theoretical model to forecast the fundamental chemical reactions involving molecular hydrogen (H₂), which has remained largely unpredicted and unsolved by scientists for many decades.

“Chemical reactions are the basis of life, so predicting what happens during these reactions is of great importance to science and has major implications in innovation, industry and medicine,” said Zammit, who earned his doctoral degree in physics from Curtin and is currently a postdoctorate fellow at Los Alamos National Laboratory, USA. “Our model is the first to very accurately calculate the probability of fundamental electron-molecular hydrogen reactions.”

Molecular hydrogen — two hydrogen atoms bound together — is the most abundant molecule in the universe, with a presence in interstellar space and in the atmospheres of gas giants. In interstellar space, solar winds (a source of electrons) collide with gas clouds of H₂, which then emit light. This light carries vital information about past events in the universe.

To decipher this information, Zammit and his team from Los Alamos and Curtin looked at the underlying chemical reaction that took place — an electron colliding with H₂. Starting from the first principles of quantum mechanics and utilising supercomputers, they developed a program to calculate the probability of chemical reactions, such as the ionisation (removal of an electron) or electron excitation of a molecule.

Their results for electrons colliding with H₂ are consistent with other experiments and will have direct implications in the modelling of fusion plasmas, the design of aerospace materials (for atmospheric entry), astrophysics and atmospheric modelling. The results will also be used to understand basic questions about nature, such as the cooling mechanisms of the early universe and the formation of planets and stars.

The research has been published in the journal Physical Review Letters and will be the subject of several presentations at international conferences and coordinated research projects this year. Zammit and his colleagues are meanwhile turning their attention to other molecules of astrophysical, medical and industrial importance, as well as extending the method to model molecular collisions with positrons, protons and antiprotons.