A new endstation for extreme-ultraviolet spectroscopy of free clusters and nanodroplets

Björn Bastian; Jakob D. Asmussen; Ltaief Ben Ltaief; Achim Czasch; Nykola C. Jones; Søren V. Hoffmann; Henrik B. Pedersen; Marcel Mudrich

doi:10.1063/5.0094430

arXiv · 2204.04094

A new endstation for extreme-ultraviolet spectroscopy of free clusters and nanodroplets

Björn Bastian·Jakob D. Asmussen·Ltaief Ben Ltaief·Achim Czasch·Nykola C. Jones·Søren V. Hoffmann·Henrik B. Pedersen·Marcel Mudrich

View original source ↗Read source document ↗Export metadata ↓

Abstract

We present a new endstation for the AMOLine of the ASTRID2 synchrotron at Aarhus University, which combines a cluster and nanodroplet beam source with a velocity map imaging and time-of-flight spectrometer for coincidence imaging spectroscopy. Extreme-ultraviolet spectroscopy of free nanoparticles is a powerful tool for studying the photophysics and photochemistry of resonantly excited or ionized nanometer-sized condensed-phase systems. Here we demonstrate this capability by performing photoelectron-photoion coincidence (PEPICO) experiments with pure and doped superfluid helium nanodroplets. Different doping options and beam sources provide a versatile platform to generate various van der Waals clusters as well as He nanodroplets. We present a detailed characterization of the new setup and present examples of its use for measuring high-resolution yield spectra of charged particles, time-of-flight ion mass spectra, anion-cation coincidence spectra, multi-coincidence electron spectra and angular distributions. A particular focus of the research with this new endstation is on intermolecular charge and energy-transfer processes in heterogeneous nanosystems induced by valence-shell excitation and ionization.

Explore related subjects

physics.atm-clus

Keep this discovery

BibTeX RIS

Björn Bastian, Jakob D. Asmussen, Ltaief Ben Ltaief, Achim Czasch, Nykola C. Jones, Søren V. Hoffmann, Henrik B. Pedersen, Marcel Mudrich. 2022-04-08. A new endstation for extreme-ultraviolet spectroscopy of free clusters and nanodroplets. https://doi.org/10.1063/5.0094430

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Core-Level Spectroscopy Decodes Bond-Alternation Dynamics of Cyclo[18]Carbon

The advent of X-ray free-electron lasers and high-harmonic generation has made time-resolved X-ray spectroscopy a powerful tool for probing local atomic environments, yet whether localized core excitations can report on global collective distortions remains open. Cyclo[18]carbon (C$_{18}$), with its polyynic ground state (D$_\text{9h}$) and cumulenic transition state (D$_\text{18h}$), provides an ideal model to address this long-standing issue in bond-length alternation (BLA) dynamics. Mapping two-dimensional potential energy surfaces by first-principles simulations, we find that core ionization symmetrizes the ground-state double-well potential along the BLA coordinate. Our calculated X-ray spectra reveal remarkable sensitivity to bond-length variations: C1s ionization potentials vary by up to 2.4~eV across the BLA coordinate (1.1--1.4~\AA), with a 0.9~eV variation for minima predicted by different functionals, while NEXAFS $\pi^*$ peaks shift by up to 4~eV across the same coordinate. These predicted signatures provide a quantitative spectroscopy--structure dictionary for decoding transient structures in future ultrafast X-ray experiments and monitoring bond-alternation dynamics in real time.

physics.atm-clus↗

arXiv2026

X-ray photoelectron spectroscopy of Ar and Kr clusters formed in He nanodroplets

We report the first soft x-ray photoelectron spectroscopy (XPS) measurements of Ar and Kr clusters formed inside superfluid helium nanodroplets (HNDs) through consecutive pickup of dopant atoms. Ar and Kr atoms and clusters are selectively inner-shell ionized (Ar 2p, Kr 3d) using monochromatic soft x-ray synchrotron radiation. In the regime of strong doping, the electron spectra exhibit features characteristic of free Ar and Kr atoms as well as their clusters. The Kr cluster spectra agree well with literature data for bare Kr clusters. Backed by detailed simulations of the pickup process, this agreement indicates that the observed spectra originate from nearly bare Ar and Kr clusters, from which most or all He has evaporated in the course of cluster aggregation. These results establish HNDs as a platform for XPS of various types of molecular complexes and nanostructures.

physics.atm-clus↗

arXiv2026

What is superatom?

The term "superatom" was introduced over three decades ago to describe clusters that emulate elemental atoms. The field has long been guided by the spherical jellium model, where magic numbers arise from shell closure of delocalized electrons. This Perspective argues that delocalization, not near-sphericity, is what makes a system atom-like. It shows that superatomic shell structure persists under arbitrary point-group symmetry, that superatomicity survives as a tunable quantum state across pressurized, ionized, and chemically precompressed systems, and that the symmetry rules governing superatoms are conditional, deeper than the jellium picture admits. The future of this field lies not in finding more magic numbers, but in exploiting superatomic states as artificial quantum systems at the atomic level.

physics.atm-clus↗