Ozone Photodissociation in the Singlet Channel at 226 nm

Area of Science:

• Physical Chemistry
• Chemical Physics
• Molecular Dynamics

Background:

• Ozone photodissociation is a key process in atmospheric chemistry.
• Understanding fragment state distributions provides insights into dissociation mechanisms.
• Previous studies have established trends in rotational distributions and anisotropy with wavelength.

Purpose of the Study:

• To investigate the rotational state distribution and vector correlations of O2 fragments from O3 photodissociation at 226 nm.
• To compare experimental results with classical trajectory calculations.
• To analyze the relationship between dissociation energy, fragment properties, and predissociation lifetimes.

Main Methods:

• Jet-cooled ozone (O3) photodissociation at 226 nm.
• Resonance-enhanced multiphoton ionization (REMPI) spectroscopy to detect O2(a 1Δg, v = 0) fragments.
• Analysis of rotational state distributions, Λ-doublet propensities, and spatial anisotropy (β).

Main Results:

• Rotational distribution shifts to higher states with decreasing wavelength, consistent with prior observations.
• Highly suppressed odd rotational state populations observed due to strong Λ-doublet propensity.
• Spatial anisotropy parameter β = 0.72 ± 0.14 for v = 0, j = 38, following the trend of decreasing β with increasing photon energy.

Conclusions:

• Experimental rotational distributions agree with classical trajectory calculations but are slightly narrower than predicted.
• v-j correlation is consistent with perpendicular orientation, though limited by depolarization effects.
• j-dependent linewidths of REMPI spectra provide information on the lifetime of the resonant O2(d 1Πg) state influenced by predissociation.