LINKEDIN: Iain McNab
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Prof. John C. Polanyi at the University of Toronto.
Our work is nanoscience - researching into nano-patterning, while studying fundamental photochemistry and molecular reaction dynamics (one molecule at a time) using Scanning Tunneling Microscopy and Scanning Tunneling Spectroscopy.
Electronic g/u symmetry breaking (ortho-para
mixing) in diatomic molecules
Among the most strongly forbidden transitions in homonuclear diatomic molecules are pure rotation transitions. Such transitions are from para nuclear spin states to ortho nuclear spin states. We have recently become interested in the fact mixing between ortho and para modifications of molecules causes such transitions to gain intensity. This ortho-para mixing is caused by the nuclear hyperfine hamiltonian and becomes more intense as ortho and para states are in closer proximity. Close to a degenerate dissociation limit of a homonuclear diatomic molecular ion there are always ortho and para states in close proximity. This mixing has implications in Bose Einstein condensation, low energy scattering and photoassociation spectroscopy. Our approach looks at the problem by examining transitions to states close to a degenerate dissociation limit which only have intensity because of the ortho-para mixing. We have measured a forbidden pure rotation transition in H2+ in the last vibrational level of the electronic ground state, with excellent agreement between our measurements (Physical Review Letters, 86, 1725-1728, 2001) and the predictions of Dr Richard E Moss and Dr Phil Bunker.
Spectroscopy of Molecular Dications
Our research used a combination of infrared laser spectroscopy and mass spectrometry to obtain structural information about simple molecules with a double positive charge (molecular dications). We obtained high resolution infrared measurements of a molecular dication (DCl2+). This work was described as a "world first" by the EPSRC . For DCl2+ we have succeeded in obtaining hyperfine information (which arises due to interactions of nuclear spins and other various intrinsic angular momenta within the molecule); the first hyperfine information ever to be measured for a molecular dication (Physical Review A, Rapid Communication, 61, 50501-1 to 50501-4, 2000). We also measured the first ever Zeeman splittings to be seen for a molecular dication (Journal of Physics B, 35, L237-L244, 2002)
Spectroscopy of H3+
H3+ is one of the most important molecules in the universe! It is believed to be the driving force behind almost all interstellar chemistry by acting as a proton donor to neutral atoms and molecules, enabling them to take part in a series of reactions until a charge neutralisation event occurs. The spectroscopy of H3+has been the subject of two Royal Society Discussion Meetings (2000 and 2006).