Vibrational Quenching of Optically Pumped Carbon Dimer Anions

Area of Science:

• Quantum information science
• Molecular physics
• Quantum chemistry

Background:

• Precise control of quantum states is crucial for quantum information, quantum-controlled chemistry, and astrophysics.
• Optical control of molecular ions is challenging due to limited suitable energy level schemes.
• Direct laser cooling has not yet been achieved for positive or negative molecular ions.

Purpose of the Study:

• To demonstrate precise optical control of the internal quantum states of carbon-2 anions (C₂⁻).
• To investigate the use of optical pumping and inelastic collisions for manipulating molecular ion states.
• To establish a foundation for future laser cooling of molecular ions.

Main Methods:

• Utilized a cryogenic wire trap to confine C₂⁻ anions.
• Employed optical pumping techniques to manipulate internal quantum states.
• Used inelastic quenching collisions with hydrogen (H₂) gas for state control and determined rate coefficients.
• Performed reduced-dimensional quantum scattering calculations for comparison.

Main Results:

• Achieved approximately 96% optical pumping efficiency into the first vibrational level of C₂⁻.
• Determined the absolute inelastic rate coefficient for v=1 to 0 collisions to be k_{q}=(3.2±0.2_{stat}±1.3_{sys})×10⁻¹³ cm³/s at 20(3) K.
• Observed fluorescence imaging of negative molecular ions using the developed techniques.
• Experimental rate coefficient was significantly smaller than theoretical predictions from quantum scattering calculations.

Conclusions:

• Demonstrated high control over a cold ensemble of C₂⁻ anions.
• The developed methods provide a robust foundation for advancing laser cooling techniques for molecular ions.
• Optical pumping and inelastic collisions are effective tools for manipulating molecular ion quantum states.