Action number: CA21101
Grantee name: Olga V. Lushchikova
Details of the STSM
Title: Bond dissociation energies of lanthanide metal complexes
Start and end date: 24/03/2023 to 10/04/2023
Description of the work carried out during the STSM
During the stay in the lab of Prof. Armentrout (U. Utah, USA) the applicant has learned how to perform collision-induced dissociation (CID) measurements using guided ion beam mass spectrometry in order to determine bond dissociation energies (BDEs). Originally it was planned that as an example TbO+ will be studied. Instead, SmO+ was used. In general, the change in the studied system has not influenced the final goal of the STSM. Additionally, an attempt was made to determine the BDE of the CuCO2+ complex, the system which the applicant will study in her home lab. However, it appeared to be difficult to make in the discharge source.
To determine the BDE of SmO+, the Sm+ ions are produced in the discharge source. Further, O2 is added to the chamber to create SmO+ complexes, which are then thermalized by collisions with Ar and mass-selected by the magnetic sector deflector. The selected precursor ion is further decelerated to desired kinetic energy and injected into the octupole guide cell, also called the collision cell. The collision cell is filled with the neutral gas to perform CID. Finally, the fragments formed during the collision of the selected ion with the gas in the collision cell are detected as a function of the ion energy with the quadrupole mass spectrometer.
To obtain correct BDEs the zero-point energy, E0, of the system should be determined by looking at the energy at which the parent ion can be transmitted through the collision cell without reaction gas. Then the fragments are determined by filling the collision cell with the neutral reaction gas and selecting high collision energy (typically above the expected BDE energy recalculated to the lab frame energy, EBDE, lab). Once E0 is determined and the fragments are identified, the energy scans (typically from E0-1 eV to EBDE, lab+5 eV) can be done. For each energy, the intensity of the parent and the fragments is measured with filled (foreground signal) and empty collision cells (background signal). The reaction of SmO+ with three reaction gasses has been studied during STSM: Ar, Ne and SO2.
The obtained data is then analysed with in-house written software CRUNCH. This software allows manipulation and fitting of the obtained curves. The data is first normalised for E0 and the background signal. Then, the intensities are recalculated to the cross-sections and lab-frame energies to the centre of mass energies. Further, the modified data is fitted considering rotational and vibrational energies, which can be either estimated or calculated. The successful fit allows us to accurately define the BDE.
The collisions with Ar, Ne and SO2 resulted in the fragmentation of SmO+ to Sm+ and O fragments. The Sm-O BDEs are 5.7, 3.2 and 5.5, respectively. However, such a big difference in Ne measurements is unexpected. Therefore, additional calculations and measurements will be performed to understand the cause of this deviation.
Description of the STSM main achievements and planned follow-up activities
The main goal of STSM was to learn how to perform CID measurements in order to obtain BDE and it was successfully achieved. By performing several experiments grantee has learned the main principles, experimental setup and data analysis software. The fruitful discussions with the members of the host group also helped the grantee to get an idea of how to implement collision cell for the CID measurements in her experiment in the correct way. Additionally, the data obtained during this stay will be analysed by the grantee and might lead to a paper.
The instrument in the grantee’s home lab will be modified as the next step. Then BDEs of test systems will be measured and results will be compared to that obtained in Armentrout’s lab. This comparison will help to estimate the effective length of the collision cell, which is different from the physical cell length, and see whether correct BDEs can be obtained. Once the instrument is working correctly more complex systems that cannot be produced with a discharge source will be studied. Of particular interest are the cationic and anionic metal cluster complexes with H2 and CO2. The data analysis will be done in collaboration with Armentrout’s group. The grantee has also submitted an FWF proposal, a part of which is dedicated to the accurate BDE determination of the M+/–CO2 (with M=Ni, Cu and Cu/Ni clusters from 1 to 10 atoms).
In summary, combining the expertise of the two labs will create new research directions. The use of a superfluid He nanodroplet source will enable accurate determination of BDEs of a wide variety of positively and negatively charged systems, which is not possible with other methods. This will give the grantee, a young female researcher, an opportunity to establish her independent research line, which is an important step in her scientific career.
Current STSM made it possible to obtain the required knowledge to study the stability and chemical reactivity of the mono- and bimetallic clusters of different sizes, charges and compositions (WG 3). Moreover, experimentally obtained BDEs could be used as a benchmark for theoretical calculations (WG 1). In the future, the most catalytically active clusters will be identified in the gas phase prior to depositing and compared to their deposited counterparts. WG 4 will also benefit from the knowledge obtained with the upgraded instrument, as it introduces a new possibility to study tailor-made metal clusters formed in the superfluid He nanodroplets.