Time-resolved crossed-beam thermal lens measurement as a nonintrusive probe of flow velocity

Abstract
A simple theory is generated for crossed-beam thermal lens and photothermal deflection in flowing sample streams. This theory is used to analyze time-resolved crossed-beam thermal lens data. The result of the regression analysis may be used as a good probe of flow velocity in the 0.2–30-mm/sec range in liquid streams. Faster flow velocity should be measurable in gas streams.