Research Highlights
(a) Exploration of an exotic phenonmenon: Intermolecular Coulombic Decay (ICD)
Intermolecular Coulombic Decay (ICD) is a mechanism whereby excited
molecules in weakly bound systems, such as clusters, relax by ionising their
neighbours. It is a non-local analogue of Auger decay, as shown in this
schematic below.
Figure: In the left, an inner-shell vacancy (2s hole) in one Ne atom of Ne-dimer is
initially created. This hole is filled by a valance electron and the excess energy in the
system ionizes the neighbouring unit of the dimer.
Following its prediction in 1997 by Prof. Lorentz Cederbaum, numerous beautiful experiments measured ICD in clusters. Bibliography on all the works on ICD can be found here. Recently, we observed an unusual ICD that occurs even between unbound molecules! Our work shows that this unusual ICD is characteristic of π-molecules which constitutes our biochemical environment. This work was published in Nature Chemistry and also appeared on Nature Chemistry’s cover page!
Figure: Three unbound pyridine molecules undergo photoexcitation. In their excited states their undergo associative interaction which binds them into a trimer. En route to the associate two molecules tranfer their energy to the third and ionizes it via ICD!
Figure: Our work on ICD on Nature Chemistry’s cover page
More interesting results on ICD are to appear soon! We are currently exploring such exotic ICD processes in unbound environments!
Ph.D. project availability: This project has a vacany and the new student will study the role of Intermolecular Coulombic decay in negative ions and in the formation of new molecules..
(b) Probing the structure of an anion using Velocity Map Imaging
Although numerous molecules and positive ions are detected in the ISM, only six anions have been detected in the ISM. The reason for this is that the low temperature and low density environment on the ISM is not favourable for several known mechanisms of formation of anions. We study the formation pathways of anions and with our recent experiments we have shown that excitation of large anions to their rsonance could result in the formation of smaller anions in the ISM and when a molecule with high dipole moment captures a free electron to form dipole bound resonances then there is a possibility to form a stable negative ion state of that molecule. We had built a state of the art Velocity Map Imaging (VMI) technique to study these formation pathways.
Ph.D. project availability: This project has a vacancy and the new student will study the formation pathways for negative ions is ISM.
We have built a state-of-the art iontrap experimental setup. The iontrap is a 22-pole radiofrequency iontrap in which we can trap low energy ions of both polarities. We study low-energy collision reactions within the trap to probe the formation of ISM anions in space.
Ph.D. project availability: This project has a vacancy and the new student will study the role of Intermolecular Coulombic decay in pi-molecules in forming larger molecules starting from smaller ones.