A 4 K FT-ICR cell for infrared ion spectroscopy

Abstract

We present the design of the newly constructed cryogenic Fourier-transform ion cyclotron resonance (FT-ICR) ion trap for infrared ion spectroscopy. Trapped ions are collisionally cooled by the pulsed introduction of buffer gas into the cell. Using different buffer gases and cell temperatures, we record action spectra of weakly bound neutral gas-analyte complexes with an IR laser source. We show for the first time that ion-He complexes can be observed in an ICR cell at temperatures around 4 K. We compare the experimental vibrational spectra of Ag(PPh) obtained by tagging with different neutral gases: He, Ne, Ar, H, and N to computed vibrational spectra. Furthermore, the conditions necessary for the formation of neutral tags within an ICR ion trap are studied.

A Universal Quantitative Descriptor of the Dispersion Interaction Potential

“…Cryogenic spectroscopy allows the isolation of weakly bound complexes of molecules with so‐called tag molecules, that is, noble gases or small molecules such as dinitrogen . These complexes can be analyzed directly or utilized for infrared photodissociation (IRPD) experiments . In IRPD, the complexes are cleaved by absorption of photons, which can be recorded by photon intensity changes or by detection of the generated fragments.…”

Cryogenic ion vibrational predissociation (CIVP) spectroscopy of a gas-phase molecular torsion balance to probe London dispersion forces in large molecules

“…Equally important is the strong, IR-active, N-H stretching mode-the reporter chromophore-which lies in a convenient spectral region well-separated from those for other vibrations, that is readily accessible by non-linear frequency mixing techniques with pulsed laboratory lasers. 9 The identity of the band can always be checked by H/D exchange, which is experimentally trivial to perform. Examination of the experimental CIVP spectrum, and the computed IR spectra, in Figure 6 show that the N-H frequency is sensitive to the proximity of the aryl moiety, presumably because of an N-H/aryl cation- interaction.…”

A Universal Quantitative Descriptor of the Dispersion Interaction Potential

“…Cryogenic spectroscopy allows the isolation of weakly bound complexes of molecules with so‐called tag molecules, that is, noble gases or small molecules such as dinitrogen . These complexes can be analyzed directly or utilized for infrared photodissociation (IRPD) experiments . In IRPD, the complexes are cleaved by absorption of photons, which can be recorded by photon intensity changes or by detection of the generated fragments.…”