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.

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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: 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.

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: 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: 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.