This week, we at the DESIREE infrastructure hosted our first official external users: James N Bull and Michael Scholz from the University of Melbourne School of Chemistry.
Who are you; where are you from?
Dr James Bull and Mr Michael Scholz from the School of Chemistry at the University of Melbourne in Australia – about as far away from DESIREE as you can get!
What is your research in general?
We study gas-phase photochemical dynamics using action spectroscopy. This involves coupling lasers with mass spectrometry, including tandem ion mobility mass spectrometry coupled with nanosecond lasers to investigate ‘shape selected’ chemistry (geometric isomers, tautomers or different deprotonation/protonation site). We are also interested in ultrafast excited state dynamics, which can be indirectly fingerprinted using nanosecond lasers or directly clocked using femtosecond pump-probe strategies. Our research impacts diverse subject areas such as astrochemistry, biophysical chemistry, and technological materials.
How will your experiments at DESIREE further your research?
Recently, we were awarded a STINT exchange grant with Dr Mark Stockett, a local user of DESIREE. Our collaboration involves studying the photophysics of anions thought to exist in space. For example, only six polyatomic anions are known to exist in the interstellar medium (C2nH-, n=2-4 and C2n-1N-, n=1-3), all of which were discovered over a six-year period through comparison of astronomical spectra with high-resolution laboratory measurements. The discovery of other anions is probably thwarted by a lack of detailed spectroscopic and dynamical information, including radiative cooling rates, statistical electron ejection rates, and electronic internal conversion efficiencies. We are applying a multi-faceted action spectroscopy approach to understand anion formation and cooling mechanisms, stabilities/resilience, and excited state dynamics of both known and highly probable (e.g. polycyclic aromatic hydrocarbon) astronomical anions. Ultimately, these data will guide discovery of new anions in space and provide critical data for sophisticated astrochemical models. Our current measurements at DESIREE utilise the caesium sputter source and cryogenic cooling (symmetric ring), allowing measurement of precise detachment thresholds (adiabatic electron affinities) and cooling rates.
Are there any unique capabilities of DESIREE that you are exploiting?
The principal advantage of DESIREE for this trip was cryogenic cooling and characterisation of cooling lifetimes. We look forward to future experiments that utilise both storage rings, allowing us to explore cold neutralisation reactions between carbonaceous anions and cations.
How do you find it to work at the infrastructure?
We have thoroughly enjoyed our time at DESIREE. The local scientists and technical staff are knowledgeable, supportive, and eager for users to get the most out of their beamtime. Our accommodation at the Wenner-Gren centre as guest scientists was both convenient and flexible for the long hours of data collection.