Calcium-containing diatomic dications in the gas phase

Area of Science:

• Physical Chemistry
• Atomic and Molecular Physics
• Materials Science

Background:

• Sputtering of calcium-containing samples with energetic oxygen beams has yielded novel diatomic dications.
• Previous theoretical studies predicted the stability of some calcium halide and hydride dications.
• Experimental observation of CaF2+ and CaBr2+ was previously reported, but other species remained uncharacterized.

Purpose of the Study:

• To experimentally produce and identify novel diatomic calcium dications.
• To theoretically investigate the electronic structure and stability of CaSi2+, CaP2+, and CaF2+.
• To characterize the dissociation channels and thermodynamic properties of these molecular ions.

Main Methods:

• Ion surface bombardment (sputtering) using a 17 keV, high-current 16O- beam.
• Identification of diatomic dications using positive ion mass spectrometry and time-of-flight measurements.
• High-level ab initio electronic structure calculations for characterizing electronic states and stability.

Main Results:

• Experimental production and mass spectral identification of CaSi2+, CaP2+, CaF2+, CaH2+, CaCl2+, CaBr2+, and CaI2+.
• Theoretical confirmation of thermodynamic stability for CaF2+ and CaP2+, and metastability for CaSi2+.
• Determination of equilibrium internuclear distances, well depths, dissociation energies, and barrier heights for the studied dications.

Conclusions:

• The study successfully produced and characterized several novel diatomic calcium dications.
• CaF2+ and CaP2+ are thermodynamically stable, while CaSi2+ is metastable.
• The findings provide valuable insights into the stability and properties of multiply charged diatomic molecules.