Analysis of the A∼-X∼ electronic transition of the 2,1-hydroxypropylperoxy radical using cavity ringdown spectroscopy

► Organic peroxy radicals are important reactive chemical intermediates in tropospheric oxidation. ► The NIR electronic spectrum of 2,1-hydroxypropylperoxy radical is observed. ► The origin and vibrational bands of the three most stable conformers are observed and assigned.