Unusual Quartet-Doublet Phosphorescence from the Phosphaethynyl Radical, CP

Area of Science:

• Molecular Spectroscopy
• Photochemistry
• Quantum Chemistry

Background:

• The phosphaethynyl radical (C₂PH) is a key molecule in astrochemistry and combustion.
• Understanding its photophysical properties is crucial for interpreting interstellar spectra and reaction mechanisms.

Purpose of the Study:

• To report the first detection of phosphorescence from the phosphaethynyl radical.
• To investigate the mechanism of quartet-doublet emission in this radical.

Main Methods:

• Matrix isolation spectroscopy in solid argon.
• Photolysis and spectroscopic analysis of the phosphaethynyl radical.
• Lifetime measurements of the phosphorescence emission.

Main Results:

• First observation of phosphorescence from the phosphaethynyl radical.
• Identification of quartet-doublet emission, likely facilitated by intersystem crossing.
• Characterization of vibronic progressions for specific electronic transitions.
• Measured phosphorescence lifetime of 108 ± 3 ms.

Conclusions:

• The study demonstrates efficient intersystem crossing in the phosphaethynyl radical.
• The observed phosphorescence provides valuable data for theoretical modeling and astrophysical observations.
• This work expands the understanding of photophysical processes in small radicals.