A new velocity-map imaging apparatus equipped with a laser-vaporization supersonic cluster source and a time-of-flight mass spectrometer is described for high-resolution photoelectron spectroscopy studies of size-selected cluster anions. Vibrationally cold anion clusters are produced using a laser-vaporization supersonic cluster source, size-selected by a time-of-flight mass spectrometer, and then focused co-linearly into the interaction zone of the high-resolution velocity-map imaging (VMI) system. The multilens VMI system is optimized via systematic simulations and can reach a resolution of 1.2 cm−1 (FWHM) for near threshold electrons while maintaining photoelectron kinetic energy resolutions (ΔKE/KE) of ∼0.53% for higher energy electrons. The new VMI lens has superior focusing power over a large energy range, yielding highly circular images with distortions no larger than 1.0025 between the long and short radii. The detailed design, simulation, construction, testing, and performance of the high-resolution VMI apparatus are presented.

Recent developments in attosecond technology led to table-top x-ray spectroscopy in the soft x-ray range, thus uniting the element- and state-specificity of core-level x-ray absorption spectroscopy with the time resolution to follow electronic dynamics in real-time. We describe recent work in attosecond technology and investigations into materials such as Si, SiO₂, GaN, Al₂O₃, Ti, and TiO₂, enabled by the convergence of these two capabilities. We showcase the state-of-the-art on isolated attosecond soft x-ray pulses for x-ray absorption near-edge spectroscopy to observe the 3d-state dynamics of the semi-metal TiS₂ with attosecond resolution at the Ti L-edge (460 eV). We describe how the element- and state-specificity at the transition metal L-edge of the quantum material allows us to unambiguously identify how and where the optical field influences charge carriers. This precision elucidates that the Ti:3d conduction band states are efficiently photo-doped to a density of 1.9 × 10²¹ cm⁻³. The light-field induces coherent motion of intra-band carriers across 38% of the first Brillouin zone. Lastly, we describe the prospects with such unambiguous real-time observation of carrier dynamics in specific bonding or anti-bonding states and speculate that such capability will bring unprecedented opportunities toward an engineered approach for designer materials with pre-defined properties and efficiency. Examples are composites of semiconductors and insulators like Si, Ge, SiO₂, GaN, BN, and quantum materials like graphene, transition metal dichalcogens, or high-Tc superconductors like NbN or LaBaCuO. Exiting are prospects to scrutinize canonical questions in multi-body physics, such as whether the electrons or lattice trigger phase transitions.

We report high resolution photoelectron spectra of Au2− using a newly built photoelectron imaging apparatus. Vibrationally resolved photoelectron images are obtained for the ground state detachment transition of Au2− at various photon energies (442.80–670.18 nm) at a resolution of 3 cm−1 for low energy electrons. Franck-Condon simulations yield the vibrational temperature of Au2− and the high resolution data yield accurate spectroscopic constants for the ground states of Au2 and Au2−. The electron affinity of Au2 is measured to be 1.9393 ± 0.0006 eV. A more precise value for the Au2− dissociation energy is also obtained as 1.937 ± 0.005 eV.

Numerous studies have suggested that the n→π* interactions between carbonyls could contribute significantly to the stability of proteins. Nevertheless, their evaluation is challenging because of the solvent environment or crystal packing forces in solids. Here we study the rotational spectrum of HGlyProOH dipeptide, a very common sequence found in collagen, the most abundant protein in vertebrates, in isolated conditions. Three different structures are unequivocally characterized in the gas phase. Interestingly, the most abundant structure is stabilized by an n→π* interaction and adopts the same conformation as is found in crystalline collagen. This observation serves to support the importance of the n→π* interactions between carbonyl groups.

Propofol (2,6-diisopropylphenol) is a broadly used general anesthetic. By combining spectroscopic techniques such as 1- and 2-color REMPI, UV/UV hole burning, infrared ion-dip spectroscopy (IRIDS) obtained under cooled and isolated conditions with high-level ab initio calculations, detailed information on the molecular structure of propofol and on its interactions with water can be obtained. Four isomers are found for the bare propofol, while only three are detected for the monohydrated species and two for propofol·(H₂O)₂. The isopropyl groups do not completely block the OH solvation site, but reduce considerably the strength of the hydrogen bonds between propofol and water. Such results may explain the high mobility of propofol in the GABA_A active site, where it cannot form a strong hydrogen bond with the tyrosine residue.