MEASUREMENTS OF THE OH-A-X(0,0) 306NM ABSORPTION BANDHEAD AT 60-ATM AND 1735-K

The R-branch bandhead near 306.5 nm (32,630 cm(-1)) of the OH A-X(0,0) system was measured in absorption at discrete frequencies for the con dition 1735 K and 60 atm. Mixtures of dilute H-2/O-2 in argon reacted in the reflected-shock region of a high-pressure, high-purity shock tu be to form transient concentrations of OH. Absorption was measured usi ng the narrow-linewidth laser light provided by a frequency-doubled ri ng dye laser. Absolute concentrations of OH were derived through a det ailed kinetics model and applied to the measured absorption to extract the absorption coefficient. A fit of the measured, composite absorpti on spectrum to one synthesized from Voigt profiles of known line stren gth and line position yielded, for the title conditions, a collision w idth (Delta nu(width)) of 2.39 +/- 0.19 cm(-1) and a collision shift ( Delta nu(shift)) of -0.83 +/- 0.11 cm(-1). Though obtained at a densit y nearly 10 times STP, the measured collision width was found to be co nsistent with the simple proportionality between Delta nu(width) and p ressure set by binary collision theory. The measured collision shift, together with other published data, was used to establish the temperat ure dependence of Delta nu(shift) through an inverse power-law. Copyri ght (C) 1996 Elsevier Science Ltd