REMPI Spectroscopy of SO Singlet States

Area of Science:

• Molecular Spectroscopy
• Quantum Chemistry
• Chemical Physics

Background:

• The sulfur monoxide (SO) radical is a key species in atmospheric and combustion chemistry.
• Understanding the electronic states of SO is crucial for reaction mechanism elucidation.
• Previous studies have primarily focused on the triplet states of SO.

Purpose of the Study:

• To identify and characterize new vibrational levels in the low-energy singlet states (a 1Δ and b 1Σ+) of the SO radical.
• To enable the first application of resonance-enhanced multiphoton ionization (REMPI) for detecting SO in these singlet states.
• To provide a revised term energy scheme connecting the singlet and triplet systems of SO.

Main Methods:

• Population of SO singlet states via two-photon dissociation of SO2 in a molecular beam.
• Detection using resonance-enhanced multiphoton ionization (REMPI) with wavelengths from 248 to 291 nm.
• Analysis of 10 rotationally resolved bands originating from a 1Δ (v=0, 6-11) and b 1Σ+ (v=8) levels.

Main Results:

• Three new vibrational levels were identified at energies 45127.88(3), 51900.40(4), and 52604.95(3) cm-1.
• Rotationally resolved spectra were analyzed for J ranging from 5 to 40/50.
• The study provides detailed rotational, vibrational, and electronic properties of the newly observed levels.

Conclusions:

• The discovery of new vibrational levels facilitates the use of REMPI for SO singlet state detection.
• A revised term energy scheme for SO is presented, integrating singlet and triplet electronic states.
• This work enhances the fundamental understanding of SO spectroscopy and electronic structure.