Assistant Professor

+44 (0)131 451 4165
Room G31
William Perkin Building
Heriot-Watt University
Roles and responsibilities
  • Erasmus exchange coordinator
  • Programme Director, Chemistry with a Year in Europe / Chemistry with a European Language

Studying Reaction Mechanisms

I study molecular reaction dynamics using complimentary experimental and theoretical methods. Experimentally I use the velocity map ion-imaging technique to measure reaction differential cross-sections. The mechanisms of a variety of atom + molecule reactions are studied theoretically using Quasi-Classical trajectories. The reaction systems currently under study are described in more detail in the research section of my website, but recent successes are described in brief below.

1. Ultrafast reaction dynamics in solution
The newest experimental strand of my research looks beyond the gas-phase to study the dynamics of solution phase reactions in 'real time' using ultrafast lasers.  Along with a team from the Bristol Laser Chemistry group, I participated in a series of ground breaking condensed phase dynamics experiments conducted at the ULTRA laser facility at the Rutherford Appleton Laboratory. A manuscript describing this work has recently been published in the journal Science.

2. Crossed molecular beam scattering of the CD3 radical
We have conducted an in depth study of the differential cross sections for rotationally inelastic scattering of methyl radicals with He, the first reported for inelastic scattering of a polyatomic free radical. Measurements made with a new crossed molecular beam and velocity map imaging instrument, were in excellent agreement with the predictions of close-coupling scattering calculations on a recently reported potential energy surface. This work has been published in Chemical Science.

3. Tug-of-War inelastic collisions in the H + D2 reaction
This work has been carried out with Eckart Wrede and in collaboration with the group of Richard N. Zare and their reaction dynamics experiment. Trajectory movies of this molecular tug-of-war which can be seen here.
This work has been published in the journal Nature.

Selected publications
  1. 'Rotationally inelastic scattering of CD3 and CH3 with He: comparison of velocity map-imaging data with quantum scattering calculations'. O. Tkáč, A. G. Sage, S. J. Greaves, A. J. Orr-Ewing, P. J. Dagdigian, Q. Ma & M. H. Alexander, Chemical Science, 2013, Advance Article, DOI: 10.1039/C3SC52002A
  2. 'Vibrationally quantum-state-specific reaction dynamics of H atom abstraction by CN radical in solution'. S.J. Greaves, R.A. Rose, T.A.A. Oliver, D.R. Glowacki, M.N.R. Ashfold, J.N. Harvey, I.P. Clark, G.M. Greetham, A.W. Parker, M. Towrie & A.J. Orr-Ewing, Science., 2011, 331, 1423-1426. DOI: 10.1126/science.1197796.
  3. 'Velocity map imaging of the dynamics of bimolecular reactions'. S.J. Greaves, R.A. Rose and A.J. Orr-Ewing, Phys. Chem. Chem. Phys., 2010, 12, 9129. DOI: 10.1039/C001233E
  4. 'Vibrational excitation through tug-of-war inelastic collisions'. S. J. Greaves, E. Wrede, N. T. Goldberg, J. Zhang, D. J. Miller, R. N. Zare, 2008, 454, 88-91. DOI: 10.1038/nature07079 
Further information