OH formation dynamics in 193 nm photolysis of 2-methoxyethanol: A laser induced fluorescence study

Abstract

Dynamics of OH radical formation in the 193nm photolysis of 2-methoxyethanol is studied using Laser Photolysis–Laser Induced Fluorescence technique. The nascent state distribution of the OH radical is measured. The OH fragments are formed vibrationally cold, characterized by a Boltzmann-like single rotational temperature of 450±100K. The spin–orbit and Λ-doublet ratios of OH fragments are measured. The relative average translational energy of the OH channel is determined to be 17.0±3.0kcal/mol. The experimental studies along with theoretical calculations suggest a complex mechanism for OH formation consisting of at least three pathways. The prominent pathway at shorter timescale (<50ns) involves crossing over to the nearby repulsive state, whereas, at longer timescale (>1ms) involves a series of reaction with initial H3C–OCH2CH2OH bond cleavage, followed by rearrangement of OCH2CH2OH to CH2OCH2OH, and a final concerted step to generate OH and ethylene epoxide.