14 Oct 2014
The conference theme 'Towards a Molecular-Level Understanding of Atmospheric Aerosols' which took place at the Centro Stefano Franscini, Monte Verita, Ascona, Switzerland on 31 August - 5 September 2014 brought together some 30 senior scientists who each gave a 45 minute presentation on their research, as well as numerous PhD students and postdoctoral workers in their respective research groups who presented posters. The themes covered spanned a broad range of fundamental areas of physical chemistry and chemical physics, and included scientists from both theoretical and laboratory backgrounds. The major topics of the meeting included: the role of particle interfaces in chemical reactions and aerosol/gas-phase composition; the energetics, kinetics and mechanisms involved in particle nucleation; the behaviour of glassy, ultra-viscous aerosol; and the use of light to manipulate particles and probe their dynamics and composition.
My own poster was titled 'Cavity Ring-Down Spectroscopy for Single Aerosol Extinction Measurements', where I reported a new technique for the measurement of optical cross-sections at a wavelength of 405 nm for single particles. The technique involves confining a single aerosol, with a radius between 500 – 2000 nm, in a Bessel laser beam optical trap. This single particle is then manipulated and placed at the centre of a cavity ring-down beam for the measurement of its optical cross-section, composition and changes in phase/morphology. The development of such laboratory techniques and subsequent measurements are crucial in the understanding molecular processes and particle-light interactions associated with atmospheric aerosols. Narrowing down the uncertainties associated with the scattering and absorption of light by aerosol is crucial for accurate forecasting in climate models.
My poster presentation gave the opportunity to speak to people using similar techniques. I spoke extensively with members of Prof Ruth Signorell's group, who are using four Bessel laser beams to trap single aerosol particles. Such a geometry allows optical confinement with very high stability, even for non-spherical particles, allowing the measurement of freezing processes. I also met with Prof Margaret Tolbert after her inspiring talk on studies of contact nucleation process using Bessel laser beam traps. Prof Ulrich Krieger's student presented a posted on phase separation studies on microscope slides, where droplets composed of an inorganic salt mixed with an organic species were studied at a variety of relative humidities. This gave some indication of the morphologies involved in some of the phase separation work performed using our cavity ring-down set up. Such conversations have proven fruitful and have given me a firm idea of where I would like to direct my research over the final two years of my PhD.
Overall, I have been inspired by the enthusiasm and friendliness of people in the aerosol community. I have learned a lot about what the great challenges currently are in the field of atmospheric aerosol and where interest lies. I have met likeminded people with who I have remained in contact with, and who may eventually become collaborators on several projects.
The location of the conference itself, within the Swiss Alps in Ascona on Lake Maggiore, was beautiful and provided the ideal location to get away from the hustle and bustle of city life and spend some quality time to get to know colleagues and leave with a deeper understanding of the molecular processes involved in aerosol.
I would like to thank my supervisor, Prof Jonathan Reid, for giving me the opportunity to attend such a significant meeting, as well as for all the other opportunities and guidance he has provided over the last two years of my PhD research. Finally, thank you very much to the SCI-RSC Rideal Trust for their financial contribution towards travelling to this wonderful conference.
Michael Cotterell,
SCI-RSC Rideal travel award recipient
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