Spectroscopy of helium-tagged molecular ions—Development of a novel experimental setup

Abstract

In this contribution, we present an efficient and alternative method to the commonly used RF-multipole trap technique to produce He-tagged molecular ions at cryogenic temperatures, which are perfectly suitable for messenger spectroscopy. The seeding of dopant ions in multiply charged helium nanodroplets, in combination with a gentle extraction of the latter from the helium matrix, enables the efficient production of He-tagged ion species. With a quadrupole mass filter, a specific ion of interest is selected, merged with a laser beam, and the photoproducts are measured in a time-of-flight mass-spectrometer. The detection of the photofragment signal from a basically zero background is much more sensitive than the depletion of the same amount of signal from precursor ions, delivering high quality spectra at reduced data acquisition times. Proof-of-principle measurements of bare and He-tagged Ar-cluster ions, as well as of He-tagged C60 ions, are presented.

Doubly charged dimers and trimers of heavy noble gases

“…An earlier version of the apparatus 32 was recently upgraded by the implementation of a second electron impact ionizer. 31 HNDs containing some 10 6 atoms are produced in an expansion of helium gas through a 5 μm nozzle into vacuum.…”

Gas‐Phase Electronic Structure of Phthalocyanine Ions: A Study of Symmetry and Solvation Effects

“…For a more detailed description of the experimental setup, additional information can be found elsewhere. [22] From the measured mass spectra, the normalized photofragment yield Y Norm related to absorption using the following formula was calculated:…”

“…For a more detailed description of the experimental setup, additional information can be found elsewhere. [ 22 ]…”

“…This approach enables the efficient formation of weakly bound helium‐tagged molecular ions, which are suitable for gas‐phase action spectroscopy by detecting the loss of the messenger helium following photoabsorption. [ 22 ] While the UV–vis spectrum of H 2 Pc + significantly differs from that of H 2 PcD + , the formation of hydrogen bonds with water molecules results in a slight blueshift of the broad absorption bands observed in both the visible and ultraviolet regions. Through quantum chemical analysis, we rationalize the dissociation patterns and track the character of spectral features to symmetry breaking, starting from the Pc 2– conjugate base of very high symmetry (D 4h ) through H 2 Pc and open‐shell H 2 Pc + (D 2h ) to the deuterated H 2 PcD + ion (C s ).…”

Size limits and fission channels of doubly charged noble gas clusters

“…An earlier version of the experimental apparatus, described in ref. 62 and 63 was recently upgraded by adding a second electron impact ionizer after the pickup cell. 64 A schematic of the system is presented in the ESI † (Fig.…”