FRSE, EmeritusProfessor of Chemical Physics
Geoff studied for his BSc and Phd at Sheffield University. He is EmeritusProfessor of Chemical Physics. He has an international reputation in the field of gas phase molecular spectroscopy. His standing in the field has been recognised by the award of the Marlow Medal of the Faraday Division of the Royal Society of Chemistry for contributions to experimental and theoretical aspects of electronic and vibration-rotation spectroscopy, by his election to the Fellowship of the Royal Society of Edinburgh, and most recently by the award of an Emeritus Fellowship by the Leverhulme Trust. In 2000 he published a major research monograph on “Infrared Vibration Rotation Spectroscopy” (Wiley) covering much of his research area “From Free Radicals to the Infrared Sky”. He has experience in the detection and interpretation of the spectra of atmospheric trace molecules through projects funded both by the European Union, The Engineering and Physical Sciences Research Council (EPSRC) and the Natural Environment Research Council (NERC).
| e: g.duxbury strath.ac.uk | t: 0141 548 3271 | u: http://reld.phys.strath.ac.uk/ |
My research field, gas phase high-resolution molecular spectroscopy of small molecules, spans two main areas, electronic spectroscopy, and infrared spectroscopy.
The work on electronic spectra is targeted at understanding the complex coupling between electronic, vibrational and rotational motion in small free radicals and ions. Its main thrust has been the theoretical development of methods for treating the breakdown of the Born-Oppenheimer separation of electronic and nuclear motion in triatomic molecules, the Renner effect. It is based upon a method of partially decoupling electronic and nuclear motion developed with R.N. Dixon, and developed further in collaboration with J. Rostas and Ch. Jungen and A. Alijah. It has been successfully applied to calculate the energy level pattern, complex spin-orbit interaction, and anomalous life times observed in the electronic spectra of CH2 and NH2.
The research on infrared spectroscopy has two main themes, the development of new experimental techniques, primarily laser based, to allow new insights on molecular behaviour to be developed, and the applications of molecular spectroscopy related to the atmosphere of the earth. My earliest work on instrument development and spectroscopic exploitation was the development of electric resonance (laser Stark) spectroscopy, including a novel type of double resonance. Using this system, we measured laboratory spectra of one of the key interstellar molecules H2CS. We also developed one of the first efficient optically pumped submillimetre lasers.
Since then we have been involved in a number of developments in the use of diode laser spectrometers, first of all using lead salt lasers, and following on from this near infrared diode lasers, and most recently the development of a novel spectrometer based upon the use of pulsed quantum cascade (QC) lasers. QC lasers were developed in Capasso’s group at Lucent Technologies in the USA in 1994. We started our research on developing spectrometers using these lasers in 1998. Although other groups, principally in the USA, had developed spectrometers using pulsed QC lasers, we were able to develop a new type of spectrometer based upon the use of electrical pulses of a duration of between 100 nanoseconds and two microseconds during which a complete portion of a spectrum may be recorded. This led to an invitation to present our work at a SPIE Symposium in 2002, and more recently to an invited review article in “Chemical Society Reviews”.
Our work on spectroscopic applications of infrared spectroscopy was initially geared to the detection of one of the ozone destroying species, chlorine nitrate in the atmosphere. Following on from this participated in one of the definitive studies of the methyl radical. We were also involved in the EU SWAGG program to measure the absorption cross sections of the new greenhouse gases, which are likely to lead to enhancement of global warming in the future. As part of this, we extended the use of the collision cooling method for studying the rotational structure of the heavy hydrofluorocarbon molecules. Most recently, we have been applying QC laser spectrometers to measure trace quantities of gas in the atmosphere both in the natural atmosphere and in car exhausts. We have also used our spectrometer to study some of the chemical processes, which occur within the plasma in a diamond deposition system in Professor Ashfold’s group at Bristol University.
Some of the most exciting uses of QC lasers have been the unexpected discovery that our spectrometer may be used to study the non-linear behaviour of molecules exposed to a strong radiation field. This has led to our observation of rapid passage effects in low pressure gases and of free induction decay. The combination of the high power and tuneability of the QC lasers have led to our observation of these effects, which at present we are studying in detail.
Marlow Medal, Faraday Division, Royal Society of Chemistry, 1975
1/7/1972 to 30/9/1972 Visiting Scientist, Ottawa National Research Council of Canada
17/6/2004 to 13/7/2004 Visiting Scientist, Ottawa National Research Council of Canada
1/4/1984 to 5/8/1984 Professeur Associé, UER de Physique Université de Lille
1/2/1996 to 31/7/1996 JILA Visiting Fellowship University of Colorado
20/4/1998 to 15/5/1998 Visiting Professor, Lab. Photophys Molec. Université de Paris-Sud
16/5/2005 to 27/5/2005 Visiting Professor, Lab. Aimé Cotton Université de Paris-Sud
A.Cheesman, J.A.Smith, M.N.R.Ashfold, N.Langford, S.Wright, G.Duxbury, "Application of a quantum cascade laser for time-resolved, in situ probing of CH4/H2 and C2H2/H2 gas mixtures during microwave plasma enhanced chemical vapor deposition of diamond", J. Phys. Chem. A 110, 2821-2828 (2006) doi: 10.1021/jp056622u
E.Normand, M.McCulloch, G.Duxbury, N.Langford, "Fast, real-time spectrometer based on a pulsed quantum-cascade laser", Opt. Lett. 28, 16-18 (2003) doi: 10.1364/OL.28.000016
M.T.McCulloch, E.L.Normand, N.Langford, G.Duxbury, D.A.Newnham, "Highly sensitive detection of trace gases using the time-resolved frequency downchirp from pulsed quantum-cascade lasers", J. Opt. Soc. Am. B 20, 1761-1768 (2003) doi: 10.1364/JOSAB.20.001761
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