Proton transfer at subkelvin temperatures.

Area of Science:

• Physical Chemistry
• Atomic and Molecular Physics
• Low-Temperature Physics

Background:

• Ionizing delicate molecules often leads to secondary reactions and excess energy release.
• Existing methods struggle to produce intact ions from sensitive molecular species.
• Sub-kelvin temperatures offer unique environments for studying fundamental chemical processes.

Purpose of the Study:

• To demonstrate a novel, low-temperature method for ionizing molecules and molecular clusters.
• To minimize secondary reactions and excess energy during the ionization of delicate molecules.
• To prepare intact protonated molecules (XH+) for advanced spectroscopic techniques.

Main Methods:

• Utilized liquid helium nanodroplets (HNDs) as a cryogenic environment.
• Initiated protonation using pre-formed (H2)mH+ ions within HNDs.
• Introduced a proton acceptor molecule (X) in a subsequent step for controlled proton transfer.

Main Results:

• Successfully ionized molecules and molecular clusters via proton transfer at sub-kelvin temperatures.
• Achieved nascent ions with significantly reduced secondary reactions, even for delicate species.
• Demonstrated the preparation of XH+ ions suitable for messenger-tagging action spectroscopy.

Conclusions:

• The novel HND-based proton transfer method provides a gentle ionization pathway.
• This technique enables new avenues for determining proton affinities and studying ion-molecule reactions at sub-kelvin temperatures.
• The prepared XH+ ions are valuable for high-resolution molecular spectroscopy.