Latest publication from DESIREE User Jon Grumer and Gustav Eklund in Physical Review Letters. In this article, Grumer et al have measured the experimental final-state distributions for Mg atoms formed in Mg+ + D− mutual neutralization (MN) reactions at DESIREE and compared with two types of calculations: full-quantum and asymptotic model approaches. Which may describe better this MN process? Which should we choose for more complex iron group systems? Read the full article HERE.
User Profile: Daniel Strasser and Alon Bogot
Left to right: Daniel, Alon, Mathias and Richard
This week the DESIREE infrastructure hosted users from the Hebrew university of Jerusalem, Daniel Strasser and Alon Bogot. The research project aims to understand the mystery of water: what may happen when H3O+ meets OH- in gas phase, proton transfer or electron transfer? The project is in collaboration with local researchers Mathias Poline and Richard Thomas.
What is your research in general?
Mutual neutralization of molecular anions and cations.
How will your experiments at DESIREE further your research?
We will study the mutual neutralization of H3O+ + OH-
Are there any unique capabilities of DESIREE that you are exploiting?
The capability to merge trapped cation and anion beams and record the neutral products of mutual neutralization is unique to the DESIREE setup.
The trapping is essential to study of molecular species, in which internal excitation during the ionization process can be expected to affect the measured mutual neutralization mechanism.
How do you find it to work at DESIREE infrastructure?
So far so good.
User Publication: Survival of polycyclic aromatic hydrocarbon knockout fragments in the interstellar medium
Latest publication from DESIREE User Michael Gatchell in Nature Communications. In this article, Gatchell et al have studied the survival of reactive fragments of the polycyclic aromatic hydrocarbon (PAH) coronene, where individual C atoms have been knocked out in hard collisions with He atoms. Ionic fragments are stored in the DESIREE cryogenic ion-beam storage ring for up to one second. May the defective PAHs survive? Read the full paper here.
More stories behind the paper? Read the Nature blog post.
User Publication: Ultraslow cooling of carbon cluster anions
The first publication of results from an external user beamtime appeared recently in the Journal of Chemical Physics. In their article “Ultraslow radiative cooling of Cn- (n = 3 - 5)”, authors James N. Bull et al. report time-dependent photo-detachment experiments making use of the long storage lifetimes and opportunities for ion-laser interaction at DESIREE. These data are used to determine, for the first time, the infrared radiative cooling rates of isolated cluster ions on ultraslow timescales (seconds to minutes). Read the full paper here.
This is but the first of a parade of user publications expected over the next months.
DESIREE user research presented at ESD8
Moa Kristiansson (Stokcholm University) presents DESIREE user research at ESD8
The 8th International Workshop on Electrostatic Storage Devices (ESD8) was held in Tianjin, China August 26-30, 2019. The ESD conference series, held every second year since 20XX, focuses on technical developments of electrostatic ion storage rings and beam traps as well as the science these infrastructures enable. This year, several DESIREE users presented results obtained in the first two cycles of user beamtime i.e. fall 2018 and spring 2019. Among them was Stockholm University PhD student Moa Kristiansson (pictured), who presented research conducted in collaboration with Wolf Geppert (also of Stockholm University). In total, 5 oral presentations including 2 hot-topic talks, as well as several posters, were based on recent results obtained by DESIREE users. This high level of representation illustrates the productivity of the DESIREE infrastructure and the strength of its broad user community.
Upgrades for improved measurements of stored ion beam currents at DESIREE
There may be no user beamtimes at DESIREE during the summer months, but that doesn’t mean that nothing is happening! Summer is a busy period for machine upgrades and maintenance. It takes a full month just to bring the inner DESIREE vacuum chamber up to room temperature and back down to 13 K again, so every detail must be carefully planned to minimize downtime and maximize availability to users.
This summer, in addition to routine maintenance, a few notable upgrades were made to the DESIREE storage rings that may be of interest to users. These upgrades are intended to improve the measurements of stored ion beam currents i.e. the number of ions still circulating in the rings at the end of one injection cycle. These measurements are important for normalizing user data for shot-to-shot variations in injected ion current, deriving absolute cross sections, and confirming the long-time stability of ions which may have low neutral yields.
Up until now, these measurements have been performed by dumping the beam into one of two Faraday cups (labeled FCS and FCA in the picture above) located near the injection deflectors at the end of each cycle. These deflectors have been replaced with new ones of an improved design. This will eliminate the possibility of the ion beam being partially scattered off the edge of the deflector plates, instead of into the Faraday cup. This will improve the accuracy of beam current measurements for most users. Deflector plates of a similar design were installed last summer on the merging section, which was found to improve flexibility in steering the beams into and out of that section.
Speaking of the merging section, the other beam-current related upgrade this year saw fortified electrical feedthroughs connected to the “de-merging” deflectors following the merging section. This will enable users to rapidly switch the voltages on these deflectors, just like the injection deflectors currently. For very low ion currents, for example at the end of a long storage cycle, users will now be able to dump the beam onto one of the MCP detectors (the Imaging Detector ID or the Fragment Detector FD), which have far greater sensitivity than the Faraday cups.
These upgrades will open new possibilities for users to more accurately measure the current of their stored ion beams in DESIREE.
User Profile: Paul Martini
Users Paul Martini, Felix Laimer, Lorenz Kranabetter from the University of Innsbruck and Stockholm University PhD student Moa Kristansson atop the DESIREE main vessel.
This week, the first user beamtime in the 2019 calendar year, the DESIREE infrastructure hosted users from the group of Paul Scheier at the University of Innsbruck. The measurements lead by PhD student Paul Martini are aimed at measuring the electron affinity of C60-. This value has been the subject of debate for many years, and DESIREE experiments may help solve the mystery.
What is your research in general:
We research and utilize helium nano droplets to study cold chemistry and structural propitiates of molecules and clusters.
How will your experiments at DESIREE further your research?
It is important for our research to be able to compare measurements performed on isolated C60- with helium nano droplet C60-.
Are there any unique capabilities of DESIREE that you are exploiting?
We will utilize the cold temperatures and long storage times of DESIREE since this is crucial to our experiment.
How do you find it to work at the infrastructure?
Drinking coffee and eating cookies is really nice. We get to work with a lot of experts this week and get to learn a lot about all the different parts of the experiment.
User Profile: Jérôme Bernard et al.
One of the last user experiments of 2018 was conducted by an all-star team led by Jérôme Bernard from the Institut Lumière Matière at University of Lyon 1. This ambitious project demonstrates how the extreme sensitivity of DESIREE can be leveraged to explore ultraslow statistical processes in complex molecular systems.
Who are you; where are you from?
Jérôme BERNARD and Serge MARTIN from Lyon, France. Christine JOBLIN and Gabi WENZEL from Toulouse France. MingChao JI from Toulouse, France at time of the application and recently hired as a Post-doc in Stockholm University
What is your research in general?
In Lyon, our present research, we aim to study the properties of PAH (Polycyclic Aromatic Hydrocarbons) cations on long time scale using electrostatic ion storage rings. In Lyon, we have built a compact storage ring so-called the Mini-Ring, in order to store PAH cation up to 1s. Up to now, we focused on the ms range to provide evidence of the fast radiative cooling, by recurrent fluorescence, of small PAH cations such as Naphthalene, Anthracene and Pyrene. Recently, we performed photodissociation spectroscopy on dimers of PAHs. We aim to study the cooling of such species by following the width of the CR absorption band as a function of the internal energy. We collaborate extensively on these subjects with the team of Toulouse (Christine Joblin and co-workers) as they have decades of expertise in the field of PAHs.
How will your experiments at DESIREE further your research?
With DESIREE, we have access to very long storage times and very low temperatures that are not presently available with the Mini-Ring in Lyon. With DESIREE, we will have the opportunity to quantify more precisely the infrared radiative cooling rate of PAHs cations.
Are there any unique capabilities of DESIREE that you are exploiting?
Due to the very low temperature of DESIREE and the very long storage times, we expect to be able follow the radiative cooling of PAHs and small clusters of PAHs down to very low internal energies.
How do you find it to work at the infrastructure?
We spent a very good week at DESIREE, with a very friendly staff. We have appreciated the efforts made by all the people in order to provide difficult ion beams and to get the best outcome from DESIREE.
User Profile: Michael Gatchell
Michael Gatchell, Linnea Lundberg, and Simon Albertini in front of the high-energy ion source platform used to produce C60+ for their experiments.
This week the DESIREE infrastructure has been used by a team of researchers from the group of Paul Scheier at the University of Innsbruck. Led by Michael Gatchell, who has an international postdoctoral appointment jointly with Innsbruck and Stockholm University, the team is conducting the first merged beam experiments with large molecules at DESIREE. Michael also delivered an inspiring lecture on his research at Innsbruck on helium nanodroplets to the weekly SU ChemAtom seminar.
Who are you; where are you from?
Linnea Lundberg, Simon Albertini and Michael Gatchell from the University of Innsbruck in Austria.
What is your research in general?
Our main research is on the properties of clusters formed in helium nandroplets. We study everything from the structural properties of clusters to their spectroscopy.
How will your experiments at DESIREE further your research?
We have done a lot of work on both metal clusters and fullerene clusters in the past. In particular we have previously studied bond-forming reactions between gold and C60 in He droplets. Now we are aiming at studying the mutual neutralization of gold anions and fullerene cations. This will also serve as a test case for future mutual neutralization studies with fullerenes. We hope to be able to return for measurements on more astrophysical relevant systems if the experiments this week go well.
Are there any unique capabilities of DESIREE that you are exploiting?
Yes! The ability to merge ion beam at relative energies down to 0 eV is crucial for these measurements.
How do you find it to work at the infrastructure?
There are a lot of helpful people making sure that everything is working smoothly and we feel that we are in good hands.
User Profile: Paul Barklem and Jon Grumer
The past two weeks at DESIREE have been dedicated to merged beam experiments with external users from Uppsala University. Just like the railroads, DESIREE is an infrastructure which strengthens connections within Sweden as well as to the world. We spoke with Paul Barklem and Jon Grumer about their experiments and their experience as theorists using a large experimental facility.
Paul Barklem and Jon Grumer take a look beneath the DESIREE storage rings.
Who are you; where are you from?
Paul Barklem and Jon Grumer, from Uppsala University, Sweden.
What is your research in general?
We do research on theoretical atomic physics with applications to astrophysics, especially stellar atmospheres. We apply our results to measuring the abundances of chemical elements in stars, which is important information in many astrophysical problems. For example we can study how the chemical elements have been produced, as well as how our galaxy, the Milky Way, formed.
How will your experiments at DESIREE further your research?
This week we are colliding positive lithium ions with negative heavy hydrogen (deuterium) ions. This process is important in interpreting lithium abundances in stars from spectra. The inferred lithium abundances in stars tell us about the lithium produced in the Big Bang, as well about how stars evolve. The comparison of our theoretical atomic collision calculations with experiment also tests our general understanding of such atomic processes, data for which are often needed in many parts of astrophysics.
Are there any unique capabilities of DESIREE that you are exploiting?
This will be the first time such an experiment has been performed at the low collision energies relevant in stellar atmospheres.
How do you find it to work at the infrastructure?
The staff are extremely friendly, helpful, and competent. As theorists, we are inspired by what has been achieved at DESIREE, and this motivates us to do more and better calculations.
User Profile: Klavs Hansen
Klavs Hansen visits Stockholm University Department of Physics
This week’s user is Klavs Hansen, a pioneer in the use of electrostatic storage rings for cluster physics and a leader in the field of statistical physics of gas-phase nanoparticles. Also participating in this week’s beamtime was Vitali Zhaunerchyk from the University of Gothenberg Department of Physics. In addition to performing experiments at DESIREE, Klavs gave a rousing presentation at the joint Atomic and Chemical Physics seminar.
Who are you; where are you from?
Klavs Hansen, visiting from Tianjin University, P.R. China
What is your research in general?
Clusters.
How will your experiments at DESIREE further your research?
I came to Stockholm to measure the decay curves of anionic gold clusters, in particular their thermal radiation. It will help us paint the full picture of the life and deaths of gold clusters in gas phase.
Are there any unique capabilities of DESIREE that you are exploiting?
The extremely good staffing situation and friendly reception, together with the long storage capability of the ring.
How do you find it to work at the infrastructure?
Very pleasant, with a good group of very enthusiastic young scientists.
Klavs and Vitali in the DESIREE control room.
User Profile: Gustav Eklund
In yet another first, the past two weeks at DESIREE have been devoted to our first user beamtime focused on merged beams experiments. Gustav Eklund, a PhD student from Stockholm University, has been examining mutual neutralization reactions between H- and cold HD+ ions.
Who are you; where are you from?
I am a PhD student at the atomic physics group at Stockholm University. So I'm quite familiar with the facility.
What is your research in general?
As a local member of the atomic physics group I have some part in most experiments at DESIREE. My work has been mainly focused on rotational relaxation of small molecular ions that are stored in the cold environment of DESIREE. Recently I have been more involved with merged beam experiments.
How will your experiments at DESIREE further your research?
This week we are looking at mutual neutralisation of D- and HD+. We are primarily interested in investigating whether the resulting neutral HD dissociates or not, and how this potential dissociation process is dependent on the collision energy of the two beams.
Are there any unique capabilities of DESIREE that you are exploiting?
Quite a few actually! In this experiment we want to utilize DESIREE to perform merged beam experiments with positive and negative ion beams. This is one of the first merged beam experiments we are attempting so it's exciting to see how it will work out. The nice thing about performing these experiments in the cold environment of DESIREE is that the molecular ions are vibrationally and rotationally cooled as they are stored in the ring. This limits the number of available reaction channels and simplifies the results.
How do you find it to work at the infrastructure?
There is good support from the staff working here. There is always someone willing to help you with technical matters or discuss the experimental results.
User Profile: James N Bull and Michael Scholz
Left to right: Mark H Stockett, James N Bull and Michael Scholz in the DESIREE main lab.
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.
User Profile: Emma K Anderson
This week marks the beginning of user beamtime at the DESIREE infrastructure. We spoke with Emma Anderson, the Stockholm University PhD student leading this week's experiments.
Who are you; where are you from?
I’m a PhD student with the Atomic Physics group at Stockholm University and my PhD is focussed on DESIREE experiments, so I haven’t had to travel far to work at DESIREE this week.
What is your research in general?
I have been working on measuring the spontaneous decay of hot metal clusters. This week we aim to determine the dominating decay mechanism in vibrationally energetic small metal clusters.
How will your experiments at DESIREE further your research?
The experiments this week allow us to investigate the decay of small cluster anions of silver and copper with channel specificity. We would like to be able to determine if fragmentation or electron detachment is the dominant neutralisation channel in each of these small systems.
Are there any unique capabilities of DESIREE that you are exploiting?
We are able to look at the spontaneous decay for very long times due to the very low residual gas pressure of DESIREE. We are utilising three of the detectors and one of the storage rings of DESIREE to allow us to do these measurements. Previous experiments that directly measure the competition between fragmentation and electron detachment are limited.
How do you find it to work at the infrastructure?
It is a good environment to work in. There is technical and research support. This means there is always someone to help you to get the best out of DESIREE.