Two-dimensional imaging of OH laser-induced fluorescence in a flame

Abstract

A method for obtaining a two-dimensional image of laser-induced fluorescence of a naturally occurring flame radical is described. A tunable laser beam is focused by a cylindrical lens into a sheet that passes through the flame, exciting OH lying within the plane defined by the laser. The fluorescence at right angles is imaged onto an intensified vidicon tube, forming a map of the ground-state OH concentration within the flame. For a sheet 0.5 mm thick, up to 2800 counts/mm(2) of flame area are obtained on a single laser pulse for an OH concentration of 700 parts in 10(6). The method holds considerable promise for imaging in time-varying systems, such as reactive turbulent combustion.