A 4 K FT-ICR cell for infrared ion spectroscopy

Area of Science:

• Physical Chemistry
• Spectroscopy
• Analytical Chemistry

Background:

• Infrared ion spectroscopy requires efficient methods for trapping and cooling ions.
• Weakly bound complexes present challenges for spectroscopic analysis due to their fragile nature.
• Cryogenic temperatures are crucial for observing certain types of molecular interactions.

Purpose of the Study:

• To present the design and performance of a novel cryogenic Fourier-transform ion cyclotron resonance (FT-ICR) ion trap.
• To investigate the spectroscopic characterization of weakly bound neutral gas-analyte complexes using infrared laser excitation.
• To explore the feasibility of observing ion-He complexes at cryogenic temperatures within an ICR cell.

Main Methods:

• Construction and implementation of a cryogenic FT-ICR ion trap.
• Pulsed introduction of buffer gases (He, Ne, Ar, H2, N2) for collisional cooling.
• Recording infrared action spectra of trapped ions and their complexes.
• Comparison of experimental vibrational spectra with computed spectra for Ag(PPh3)2+ complexes.

Main Results:

• Demonstration of successful ion trapping and collisional cooling at approximately 4 K.
• First-time observation of ion-He complexes within an ICR cell at cryogenic temperatures.
• Acquisition of vibrational spectra for Ag(PPh3)2+ tagged with various neutral gases.
• Analysis of conditions favoring the formation of neutral tags in the ICR ion trap.

Conclusions:

• The developed cryogenic FT-ICR ion trap is effective for infrared ion spectroscopy of weakly bound complexes.
• Cryogenic conditions enable the observation of previously challenging ion-gas complexes, including ion-He.
• The study provides valuable insights into the formation and spectroscopic properties of tagged ion complexes.