Experiments with supersonic techniques: Defining hydrogen bonds and reducing ignition delays

 Supersonic compression and expansion of gases have helped in doing experiments that would have been impossible otherwise.

Water is a high boiling liquid and H2S is a stinking gas at ambient conditions and this difference was attributed to the ability of water to form hydrogen bonds with one another. This led Pauling to conclude that H already bonded to a highly electronegative element such as O, N and F can only form hydrogen bonds. This view persisted for long and appears in text books even today. Under supersonic expansion conditions ours and several other laboratories have shown that H2S can form hydrogen bonds as well. This and several other recent advances led us to form and chair an international task group on behalf of IUPAC to redefine hydrogen bonding.

Supersonic compression waves, known as shockwaves can raise the temperature and pressure of molecules to 1000s of Kelvin and 10-100 bars, respectively. This can be achieved in the laboratory using shock tubes. Our laboratory has used shock tubes not only to resolve long standing fundamental problems in chemical kinetics but also to measure ignition delays of fuels that could be of use to ISRO and DRDO. This talk will summarize both experimental techniques and the fundamental advances we have made using these well-established techniques.



About Prof. E. Arunan :

Prof. E. Arunan did his B. Sc. in American College, Madurai, M. Sc. and M. Tech degrees from IIT Madras and Delhi, respectively. He completed his Ph. D. at Kansas State University in 1991, guided by Prof. D. W. Setser. He was a postdoctoral associate of Prof. H. S. Gutowsky at the University of Illinois at Urbana-Champaign before moving to India in 1994. He has established two experimental laboratories in the Indian Institute of Science, both having unique home-built facilities. He is on the International Advisory Editorial board of Physical Chemistry Chemical Physics, published by the Royal Society of Chemistry. He is an Associate Editor of both Current Science and Journal of Chemical Sciences, published by the Indian Academy of Sciences. He is a fellow of IUPAC and the Indian Academy of Sciences.