We present on the realization of the first Bose-Einstein-Condensate of Dysprosium atoms. We present details about the experimental techniques, i.e. laser cooling and evaporative cooling, that allow us to increase the phase-space density of our gas until the onset of Bose-Einstein Condensation, signaled by the emergence of a bimodal distribution in time-of-flight.
The goal of our experiment is to study how optical cavities can modify ultracold reactions. To do so, we need to upgrade our ultracold dysprosium experiment by including two new elements in the science chamber. 1) A high-finesse optical cavity for controlling light-matter coupling. 2) An ion optics system for detecting reaction products. This requires the development of a new atomic source,...
Since 2013 the infrared FEL at the Fritz Haber Institute (FHI FEL) has been providing intense, pulsed mid-infrared (MIR) radiation, continuously tunable from <3 μm to >50 μm for in-house users. This has resulted in more than 100 peer-reviewed publications so far. In 2023 an additional short-Rayleigh-range far-infrared (FIR) FEL has been commissioned lasing from <5 μm to >170 μm. In addition, a...
In 1896, Edward Charles Pickering (1846-1919), Director of the Harvard College
Observatory (HCO), reported in a trio of publications the observation of “peculiar
spectra” of the southern star ζ Puppis, which he attributed to an “element not yet
found in other stars or on earth.” Supported by laboratory spectra obtained by Alfred
Fowler (1868-1940), Niels Bohr (1885-1962) showed in 1913...
We present a combined experimental and theoretical investigation of the radiationless decay spectrum of an O 1s double core hole in liquid water. Our experiments were carried out using liquid-jet electron spectroscopy from cylindrical microjets of normal and deuterated water. The signal of the double-core-hole spectral fingerprints (hypersatellites) of liquid water is clearly identified, with...
Photoelectron circular dichroism (PECD) has emerged as an extremely sensitive probe of the molecular and electronic structure of chiral molecules, but its suitability for application to aqueous solutions had not yet been proven. Here, we provide an update on our recent PECD measurements of aqueous-phase alanine, the simplest chiral amino acid. We demonstrate that the PECD response of alanine...
Intermolecular Coulombic decay (ICD) is a non-local autoionization process that has the potential to selectively probe the first hydration shell of solvated molecules. Here, we demonstrate the applicability of ICD spectroscopy to biomolecules in a complex environment. Firstly, we access site-specific information on the interaction of adenosine triphosphate in the aqueous phase (ATP(aq)) with...
Tens-of-µm-sized liquid jets have revolutionized experimental research on the physical chemistry of aqueous solutions. Our work on improved liquid jet techniques unlocks further interesting opportunities in this field.
We show first results of a novel set-up that enables velocity map imaging (VMI) of electrons emitted from a liquid jet, thus allowing the measurement of the full angular and...
Liquid microjets (liquid jets, LJ), introduced in the 80s–90s by M. Faubel, S. Schlemmer and J.P. Toennies, enabled the investigation of volatile liquids under high-vacuum conditions and opened a breadth of new fields [1]. One of such fields is the combination of LJs with photoelectron spectroscopy, LJ–PES, capable of revealing subtle energy shifts in molecular-orbital binding energies (BEs)...
The ytterbium monofluoride (YbF) molecule has gained attention for being a system well-suited for measuring the electric dipole moment of the electron (eEDM). In this work we present REMPI measurements of Rydberg states, i.e. states with a single (highly) excited electron, of YbF. Assignment of these measured Rydberg states to series that converge to various rotational and vibrational levels...
Photoelectron Circular Dichroism (PECD) is a chiral optical effect that manifests in the angle-dependent photoemission of an electron upon irradiation of a chiral molecule by circularly polarized light. PECD can aid in our fundamental understanding of electron dynamics as this effect is acutely sensitive to the molecular state and electron emission conditions. The magnitude and sign of PECD...
The stereochemistry and conformational flexibility of chiral molecules have a strong impact on their biological, biochemical, and pharmacological properties. A central analytical challenge is the generally applicable differentiation of enantiomers, as well as the fast and accurate determination of the enantiomeric excess of a chiral sample.
Gas phase vibrational action spectroscopy is a...
Studies on metal oxide clusters in the gas phase are aimed at gaining a better atomistic understanding of single-site catalysts. Here, we study the structure and reactivity of cationic model systems using a combination of mass spectrometry, infrared photodissociation (IRPD) spectroscopy, ion mobility and electronic structure calculations ranging from density functional theory to...
We present our recent progress on laser cooling AlF molecules using deep lasers. AlF is distinctively different from the molecular species that have been laser-cooled so far: it is a stable molecule that can be produced in large quantities and it has a strong $A^1\Pi\leftarrow X^1\Sigma^+$ transition near 227.5 nm that can be used for rapid slowing and cooling in a magneto-optical trap (MOT)...
Aluminum monofluoride (AlF) is a promising candidate for laser cooling and trapping experiments. To support research in this area, we have developed the AlF Spectroscopy Database (alf.mp.fhi-berlin.mpg.de), which features the latest spectroscopic constants for the AlF molecule across multiple electronic states.
The database is hosted on an interactive website that enables users to compute...
We have developed a Python-based toolkit designed to investigate the dynamic properties of molecular systems using molecular dynamics (MD) simulation techniques. The toolkit supports simulations under various ensembles, including the microcanonical (NVE), canonical (NVT), isoenthalpic–isobaric (NPH), and isothermal–isobaric (NPT) ensembles, enabling the study of diverse dynamic processes and...
Beyond chiral analysis, Enantiomer-Specific State Transfer (ESST) enables the control and manipulation of chiral molecules at the quantum level. Using tailored microwave fields, a chosen rotational state can be enriched for a selected enantiomer. Although ESST can theoretically achieve 100% transfer efficiency, early ESST studies reported only modest state-specific enantiomeric enrichment,...
In this poster, we present near-complete chiral selection in rotational quantum states [1]. In our study we combine UV laser and microwave radiation to realize near-ideal initial conditions for Enantiomer-Specific State Transfer (ESST). With this we overcome previous limitations of ESST due to initial thermal population in all three states in a triad of rotational states connected to the...
We present high-resolution UV spectra of three different chiral molecules — 1-Indanol, Styrene oxide and 1-Phenylethanol. All of these molecules are interesting candidates for performing experiments on enantiomer-specific quantum state control.
We show vibrationally resolved REMPI spectra together with theoretical predictions to facilitate assignment of the transitions. We also...
Gas-phase vibrational spectroscopy has been proven to provide a nearly ideal method for the investigation of ions, unperturbed by solvent effects. In addition, ions can be placed in helium nanodroplets as a matrix, where the interaction with the dopant ion is very weak. As the helium droplets are at very low temperatures (0.37 K), thermal broadening and therefore spectral congestion is...
Ultracold helium nanodroplets provide an ideal matrix for gas-phase vibrational spectroscopy, reducing thermal broadening and spectral congestion while unperturbed significantly by solvent effects and interactions with dopant ions. In the experiment, ions are embedded in a helium droplet and irradiated with a burst-mode infrared free electron laser (FEL). Resonant absorption of photons from...
Cryogenic Infrared action spectroscopy has been proven to be effective for the experimental characterization of the vibrational modes of a large variety of molecular ions and ionic clusters in the gas phase[i]. Here, the ion of interest is isolated by a quadrupole mass filter and accumulated in a hexapole ion trap, where is traversed by a beam of helium nanodroplets that pick up the selected...
Exposure of human body to ultraviolet light can induce formation of dimeric crosslinks at bipyrimidine sites within deoxyribonucleic acid. Nucleotide excision repair enzymes normally recognize the crosslinks and remove them. In-born genetic mutations of the enzymes result in severe photosensitivity and high risk of skin cancer. Completely avoiding sun or consuming medication for pain-free...
Conventional condensed-phase bioanalytical approaches often require large amounts of high-purity samples and are, therefore, not universally applicable. Mass spectrometry (MS), on the other hand, requires only minute sample amounts and its purity is often not a critical factor. Although, the extent of structural information obtained directly by MS is limited,it can be combined with...
FHI-aims (Fritz Haber Institute ab initio materials simulations) [1-3] is a versatile electronic-structure software package developed for computational studies in molecular and materials science. Widely used by a global network of developers, researchers at the Fritz Haber Institute, academic institutions, and industry, FHI-aims leverages numeric atom-centered basis sets to deliver...
A highly intricate interplay of underlying processes governs certain materials properties and functions. This prevents a realistic description by physical models or atomistic simulations. AI can identify nonlinear correlations between materials’ parameters and the measured performance. Thus, AI might better capture the materials’ behavior compared to the theory of the past. However, the data...
Sequential active learning (SAL)-driven workflows can efficiently guide experiments and simulations towards the discovery of materials with desired properties [1]. However, AI and machine-learning approaches commonly used in these workflows rely on the knowledge of key physical parameters describing the materials property of interest. These low-dimensional representations are typically...
Widely used machine-learning (ML) approaches in materials science and catalysis are designed to accurately describe, in average, a wide range of materials. Nonetheless, only a handful of compounds might show the desired properties to be suitable for a given application. Thus, global ML models may overlook these statistically exceptional materials of interest. Here, we discuss how the...
An accurate first-principles description of the electronic band structure at finite temperatures is the prerequisite to quantitatively predict the electronic and optical properties of real materials. Theoretically, this requires proper consideration of the self-energy contributions from both electron-electron (e-e) and electron-vibration (e-vib) interactions. For the latter, the widely used...
Molecular dynamics (MD) has been popularly utilized to understand the dynamical properties of materials such as thermal, electrical, and ionic conductivities. Ab initio MD provides universal, high-quality predictions for energy, forces, and stress of any material, but its usage is limited due to high computational costs. Recent machine-learned interatomic potentials (MLIPs), with their...
First-principles approaches for phonon-limited electronic transport are typically based on many-body perturbation theory [1] and thus rely on the validity of a quasi-particle picture for phonons and electrons. However, both these pictures can become questionable in strongly anharmonic systems [2,3]. We overcome this hurdle by combining ab initio molecular dynamics (aiMD) calculations with...
