Report on the outcomes of a Short-Term Scientific Mission

Action number: CA21101

Grantee name: Katrin Erath-Dulitz

Details of the STSM

Title: Time-resolved Interatomic Coulombic Decay in alkali aggregates in helium nanodroplets
Start and end date: 22/01/2023 to 03/02/2023

Description of the work carried out during the STSM

During the beamtime at ELI ERIC, we did a range of experiments with pure and with Rb-doped He nanodroplets.
The results for the studies involving pure He nanodroplets indicate that the resonant excitation of excited states in He by XUV radiation can be sufficient for nanoplasma ignition. Clear pump-probe dynamics were observed in this case. We have also investigated whether nanoplasma ignition in Kr-doped He nanodroplets is delayed with regard to laser excitation by near-infrared radiation. However, no conclusive results could be drawn from the experimental data. Likewise, we was attempted to time-resolve the ICD processes He* + Rb  He + Rb+ + eICD and He* + Rb*  He + Rb+ + eICD occurring at the surface of He nanodroplets. We did observe Rb+ formation from both the XUV pump pulses and the NIR/UV probe pulses only. However, an observed time-dependent Rb+ depletion signal which was indicative for an Interatomic Coulombic Decay process could not be reproduced. Experiments with Cs-doped He nanodroplets were started, but due to a loss of He beam signal intensity in the presence of the Cs oven in the chamber, the Cs oven was removed. The experiments with Cs and other planned activities were not resumed due to the limited amount of available beamtime.
I contributed to the beamtime mainly in terms of data analysis. For this, I wrote computer programs for the analysis of ion-time-of-flight traces and of ion-velocity-map images and I analysed the data taken. My scientific background in chemistry was invaluable with regard to the exchange of ovens for Rb and Cs doping, which I contributed to in the laboratory work. I also contributed to the discussion of the experimental results.
I also had guided tours of the experimental hall and of the L1 laser which allowed me to get a better overview of the other activities at ELI ERIC.

Description of the STSM main achievements and planned follow-up activities

The STSM contributed to the objectives of the COST Action COSY in several respects:
Scientifically, the work further shed light onto the nanoplasma ignition properties of pure helium nanodroplets which is a core topic of WG4. The analysis of the experimental data is still ongoing, so that definite interpretations cannot be made at this point. It is planned to publish the results obtained for nanoplasma ignition in a renowned scientific journal. I will also be highlighting the results at the 1st COSY General Meeting in February 2023 in Cadiz; and I will talk about my experiences with the STSM with other participants in order to steer further STSMs.
Personally, the STSM has fulfilled the goals set in advance. I have learned a lot about nanoplasma ignition, and several general tips and tricks concerning the hands-on optimization of experimental signals from pure and doped He nanodroplets. The STSM has allowed me to build and intensify collaborations with research groups from the Czech Republic, Denmark and India. The discussions steered ideas for collaborative follow-up proposals for the MAC endstation at ELI ERI, at FERMI and elsewhere. I have learned a lot about the activities at the E1 beamline at ELI ERIC, and at the MAC endstation in particular. The beamtime has allowed me to connect with the beamline scientists at the MAC endstation. The guided tour to the L1 laser has allowed me to get a better idea of the overall scopes of the institution, and about its research activities in photonics.