SF₆⁺: Stabilizing Transient Ions in Helium Nanodroplets

Area of Science:

• Physical Chemistry
• Atomic and Molecular Physics
• Chemical Physics

Background:

• Many molecular ions are too short-lived for experimental detection.
• Sulfur hexafluoride cation (SF₆⁺) has remained experimentally elusive despite numerous attempts.

Purpose of the Study:

• To develop a method for stabilizing and observing the transient SF₆⁺ ion.
• To demonstrate a versatile technique for stabilizing other short-lived molecular ions.

Main Methods:

• Doping charged helium nanodroplets (HNDs) with sulfur hexafluoride.
• Gently stripping excess helium from doped HNDs via helium gas collisions.
• High-resolution mass spectrometry (m/Δm = 15000) for ion identification.
• Collision-induced dissociation experiments.

Main Results:

• Successfully formed and observed long-lived SF₆⁺ ions.
• Ion identification confirmed by isotopic abundance and dissociation patterns.
• Optimized conditions yielded SF₆⁺ ions more abundantly than SF₅⁺ ions.

Conclusions:

• Helium nanodroplet doping provides a viable method for stabilizing transient molecular ions like SF₆⁺.
• The technique is adaptable for producing and studying other short-lived molecular ions.