Speaker
Description
Understanding the structure, chemical behaviour, and dynamics of strongly bound clusters is a central topic of our research. In the last years our molecular beam cluster experiment that is coupled to the beamline of the FHI-FEL has been extended with a laser system that now allows to apply a variety of approaches for the (vibrational) spectroscopy of neutral clusters and small metal-containing molecules using different REMPI schemes and (V)UV single-photon near-threshold ionization.
Using the approach of IR-UV two-color ionization the vibrational spectra of, e.g., small boron and iron oxide clusters have been studied. More lately the focus has been shifted towards the characterization of small dysprosium containing molecules, in preparation for experiments targeting the formation of such, yet largely uncharacterized species, via the association of ultracold atoms. As starting point, diatomic molecules like DyO, Dy$_2$, and DyCr, are investigated. For DyO, for instance, ro-vibronic spectra are obtained using 1+1 REMPI, which can be compared to earlier wavelength-resolved laser-induced fluorescence experiments[1]. Furthermore, IR absorption of the $\Omega$=8 ground state of DyO at ~839 cm$^{-1}$ is observed using the FHI-FEL. The metal dimers, the dysprosium dimer Dy$_2$ and the dysprosium-chromium dimer DyCr, are of great relevance for the preparation of ultracold molecules and the realization of a Bose-Einstein condensate of polar molecules. The many-electrons configuration of these atoms makes theoretical predictions very challenging. However, we already measured the ionization potentials of both dimers and found good agreement with our theory model. For the observation of optical transitions of these species nearly the full visible range needs to be studied. The determination of these transitions is crucial for the optical transfer scheme that is used for creating ultracold molecules by photo-association.
The IR-UV two-color ionization technique bears the potential for time resolved studies of vibrational relaxation processes in metal cluster complexes, like e.g. metal cluster carbonyls, where non-adiabatic effects related to vibronic interactions are expected to dominate the internal vibrational energy redistribution (IVR) following initial excitation, e.g. of $\nu$(C-O). Together with collaboration partners within the Max Planck – Radboud University Center for Infrared Free Electron Laser Spectroscopy we aim to study vibrational lifetimes in gas-phase metal cluster complexes using time-resolved IR-UV ionization. Thereby we will build on a recent development at the FELIX facility where the separation of single, comparably intense (>0.1 mJ), micropulses out of the macropulse circulating within the cavity of FELICE, the Free Electron Laser for IntraCavity Experiments, has been demonstrated lately[2]. In a second approach we will couple a high resolution photoelectron spectrometer to the beamline of the FHI-FEL to study time-resolved vibrational relaxation processes in anionic clusters via IR-UV two-color photodetachment. The effect of IR pre-excitation to probe otherwise non-active transitions in anion photoelectron spectroscopy has been seen only recently[3], and further motivates our efforts for such time-resolved studies.
References
1. C. Linton, D. M. Gaudet and H. Schall, J. Mol. Spec., 1986, 115, 58-73.
2. T. Janssen, C. S. Davies, M. Gidding, V. Chernyy, J. M. Bakker and A. Kirilyuk, Rev. Sci. Instr., 2022, 93, 043007.
3. M. DeWitt, M. C. Babin and D. M. Neumark, J. Phys. Chem. A, 2021, 125, 7260-7265.
| Abstract Number (department-wise) | MP 04 |
|---|---|
| Department | MP (Meijer) |
