Electronic State Spectroscopy of the Peroxychloroformyl ClC(O)OO Radical

Area of Science:

• Atmospheric chemistry
• Planetary science
• Spectroscopy

Background:

• The peroxychloroformyl (ClC(O)OO) radical is a key intermediate in Venus's atmospheric cycles.
• Understanding its reactivity is crucial for accurate photochemical modeling of Venus.
• Kinetic studies are limited due to a lack of suitable gas-phase spectroscopic methods.

Purpose of the Study:

• To investigate the electronic structure and UV-Vis spectrum of the ClC(O)OO radical.
• To provide experimental data for refining Venus's atmospheric models.
• To explore the potential for isomer-selective spectroscopic measurements.

Main Methods:

• Synergistic combination of experimental and theoretical electronic structure calculations.
• UV-Vis absorption spectroscopy using a multipass transient absorption spectrometer.
• Analysis of spectral data using Gaussian profiles and molecular orbital theory.

Main Results:

• The lowest-excited state (1^2A') of ClC(O)OO is bound, with near-infrared (NIR) excitation.
• Simulated NIR absorption bands suggest potential for cis- and trans-isomer selective measurements.
• The gas-phase UV spectrum shows a peak at 218 nm (σ ≈ 5 × 10^-18 cm^2) and a shoulder at 255 nm, assigned to specific electronic transitions.

Conclusions:

• The ClC(O)OO radical exhibits electronic structure and spectral properties consistent with other acyl peroxy radicals.
• This study provides essential spectroscopic data for atmospheric modeling of Venus.
• The findings pave the way for future kinetic and mechanistic studies of ClC(O)OO.