Absolute UV absorption cross sections of dimethyl substituted Criegee intermediate (CH3)2COO

Highlights: • Absolute UV absorption cross sections of (CH₃)₂COO are reported. • The accurately scaled UV spectra of (CH₃)₂COO as its spectral signature is characterized. • The impact of (CH₃)₂COO photolysis in the atmosphere can be quantified. • The details and uncertainties of newly developed photodepletion method are characterized. The absolute absorption cross sections of (CH₃)₂COO under a jet-cooled condition were measured via laser depletion to be (1.32 ± 0.10) × 10⁻¹⁷ cm² molecule⁻¹ at 308 nm and (9.6 ± 0.8) × 10⁻¹⁸ cm² molecule⁻¹ at 352 nm. The peak UV cross section is estimated to be (1.75 ± 0.14) × 10⁻¹⁷ cm² molecule⁻¹ at 330 nm, according to the UV spectrum of (CH₃)₂COO (Huang et al., 2015) scaled to the absolute cross section at 308 nm.