A versatile setup for studying size and charge-state selected polyanionic nanoparticles

Abstract

Using the example of metal clusters, an experimental setup and procedure is presented, which allows for the generation of size and charge-state selected polyanions from monoanions in a molecular beam. As a characteristic feature of this modular setup, the further charging process via sequential electron attachment within a three-state digital trap takes place after mass-selection. In contrast to other approaches, the rf-based concept permits access to heavy particles. The procedure is highly flexible with respect to the preparation process and potentially suitable for a wide variety of anionic species. By adjusting the storage conditions, i.e., the radio frequency, to the change in the mass-to-charge ratio, we succeeded in producing clusters in highly negative charge states, i.e., [Formula: see text]. The capabilities of the setup are demonstrated by experiments extracting electronic and optical properties of polyanionic metal clusters by analyzing the corresponding photoelectron spectra.

Metal cluster plasmons analyzed by energy-resolved photoemission

“…This can be accomplished by accelerating the electrons by a weak electrostatic potential. 32,67 Method II is based on the assumption that photodetachment fully reflects in the evolution of the weakly bound electrons and that therefore the evaluated signals are good measures of the actual cross sections. As an advantage, only the signals close to the detachment energy threshold are evaluated.…”

“…35 Special care was taken in the calibration procedure to minimize artificial electron binding energy shifts, when changing the laser wavelength. 32…”

“…Details about the experimental setup have been published elsewhere. 32 Briefly, a magnetron-based gas aggregation source is used to produce a molecular beam of clusters, which contains negatively charged silver cluster anions. 33 After size-selection, the particles enter a digital radio frequency ion trap, 34 where the anions are accumulated using argon buffer gas cooling.…”

Superconducting quantum detectors and single photon charge control for mass spectrometry

“…As the stability parameters are fixed, massive proteins require the filter to be operated at high voltages, small rod distances and at low radio frequency or using a digital voltage switching approach. 19 A quantum detector for lowly charged or even neutral massive biomolecules: We propose to extend the range of applications of superconducting nanowire detectors. A cryogenic detector capable of detecting nonfluorescent molecules across the entire mass range and at low impact energies will be a highly desirable tool for classical and quantum molecular beam research as well as for mass spectrometry.…”