Optical spectroscopy of molecular positronium

Area of Science:

• Atomic and Molecular Physics
• Quantum Chemistry
• Antimatter Physics

Background:

• Molecular positronium (Ps(2)) is a novel system composed of matter and antimatter.
• Previous studies have explored the ground state of Ps(2).
• The existence and properties of excited states of Ps(2) remain largely uncharacterized.

Purpose of the Study:

• To experimentally confirm the existence of an L=1 excited state of molecular positronium (Ps(2)).
• To perform optical spectroscopic measurements on Ps(2) to probe its excited states.
• To provide conclusive evidence for the production of this matter-antimatter system and its excited state.

Main Methods:

• Ps(2) molecules were created in a porous silica film and in vacuum from an Al(111) crystal.
• Resonant excitation of Ps(2) molecules using pulsed lasers.
• Photoionization of excited Ps(2) molecules to detect and confirm their state.

Main Results:

• Optical spectroscopic measurements provide conclusive evidence for an unobserved L=1 excited state of Ps(2).
• The study demonstrates the successful resonant excitation and photoionization of Ps(2) molecules.
• Confirmation of the production of the molecular matter-antimatter system in an excited state.

Conclusions:

• The existence of the L=1 excited state of molecular positronium is experimentally verified.
• The methods used provide a pathway for future studies of positronium-based systems.
• The photoionized vacuum L=1 Ps(2) could serve as a source for Ps(+) ions and other exotic multipositronic systems.