Shock-tube measurements of the absorption oscillator strength for the OH 2Σ→ 2Π electronic band system

Abstract

Previous shock tube measurements of the oscillator strength for the OH 2Σ→ 2Π band system made in this Laboratory (1) have been corrected. Light scattering in the absolute intensity calibration has been eliminated (1) and a continuous flushing technique was used for preparation and introduction of the water vapor-argon test gas mixture into the shock tube. (1) The experimental technique remains essentially the same as in the earlier srudies: hot gas samples of OH at 3100–3500°K were produced by the dissociation of H 2O behind the reflected shock, and the linear rate of increase of absolute spectral intensity in the transparent gas region was measured by monitoring emission from axial observations in the shock tube. The absorption electronic f-number for the 2Σ→ 2Π band system has been determined from the shock tube measurements as (3·9 ± 0·9) x 10 −3. This value should be compared with Carrington's (4) result of 1·4 x 10 −33 from absorption measurements in flames, and Oldenberg and Rieke's (5) value of 1·3 x 10 −33 and Dyne's (6) value of 0·7 x 10 −33 from measurements in absorption cells.