Newly observed low-lying Ω = 1 state of PbO

Area of Science:

• Molecular Spectroscopy
• Quantum Chemistry
• Atomic Physics

Background:

• Lead monoxide (PbO) is a diatomic molecule with complex electronic structure.
• Previous spectroscopic studies have identified several electronic states, including a1 and A0+.
• Understanding PbO's electronic states is crucial for applications in chemistry and physics.

Purpose of the Study:

• To perform high-resolution spectroscopy of lead monoxide (PbO) in the 22,400–25,300 cm−1 range.
• To identify and characterize new electronic states of PbO.
• To investigate the interactions between closely lying electronic states and their impact on spectroscopic properties.

Main Methods:

• High-resolution laser spectroscopy was employed to probe PbO molecules.
• Spectroscopic constants, including hyperfine interaction coefficients, were determined for observed electronic states.
• Analysis focused on the spectral range of 22,400–25,300 cm−1.

Main Results:

• A new Ω = 1 electronic state, designated c1, was observed between the a1 and A0+ states.
• Spectroscopic constants and hyperfine interaction coefficients were determined for the a1 and c1 states.
• Evidence of strong interaction between the vibrational levels of the a1 and c1 states was found, leading to gradual exchange of electronic state properties.

Conclusions:

• The discovery of the c1 state and its interaction with the a1 state provides new insights into PbO's electronic structure.
• The observed spectral characteristics of the c1 state raise questions regarding the current band assignment of the b0- state.
• This study contributes to a more comprehensive understanding of molecular spectroscopy and electronic interactions in diatomic molecules.