Near-Infrared Electronic Transitions of Pb(2).

Area of Science:

• Molecular Spectroscopy
• Atomic and Molecular Physics
• Quantum Chemistry

Background:

• Lead dimer (Pb2) spectroscopy is crucial for understanding heavy element electronic structures.
• Previous studies have identified several electronic states of Pb2, but detailed analysis of fine-structure transitions remains incomplete.

Purpose of the Study:

• To measure and assign new electronic transitions of Pb2 in the 5200-8500 cm(-1) range.
• To characterize the electronic energies and vibrational constants of specific Pb2 states.
• To identify and analyze purely magnetic dipole fine-structure transitions in the optical region.

Main Methods:

• Emission spectroscopy using a Fourier transform spectrometer.
• Microwave discharge of Pb(x) vapor in a H2/Ar mixture.
• Comparison with ab initio calculations for spectral assignment.

Main Results:

• Two new electronic transitions of Pb2 were measured and assigned to transitions from the lowest 1(g) and 1(u) states to the X(1)0(+)(g) ground state.
• The X(2)1(g) --> X(1)0(+)(g) transition was identified as the first purely magnetic dipole fine-structure transition in the optical region.
• Electronic energies and vibrational constants for the X(1)0(+)(g), X(2)1(g), and A(2)1(u) states of (208)Pb2 were determined with high precision.

Conclusions:

• The study provides a detailed spectroscopic characterization of new electronic transitions in Pb2.
• The identification of a purely magnetic dipole fine-structure transition advances the understanding of molecular spectroscopy in heavy elements.
• The obtained spectroscopic constants will aid in theoretical and experimental investigations of Pb2 and related molecules.