With a first application of semiconductor lasers to absorption measurements of seeded atomic Rb in high-enthalpy flow fields, a diagnostic technique for time-resolved determination of flow velocity and gas temperature with a line-shape analysis was developed. In our measurements a GaAlAs diode laser was used to scan repetitively at 15 kHz over 1.3 cm<sup>−1</sup> across the D<sub>2</sub> resonance transition (5<i>S</i><sub>1/2</sub> → 5<i>P</i><sub>3/2</sub>, 780.2 nm) of seeded atomic Rb to obtain multiple absorption line shapes. The time-dependent signal contains highly resolved spectral line-shape information, which we interpret by fitting the spectrally resolved line shapes to Voigt profiles. Kinetic temperatures in the range 900–1400 K and gas velocities in the range 3900–6200 ms<sup>−1</sup> were obtained from the Doppler-broadened component of the line shape and from the Doppler shift, respectively, of the absorption frequency.
© 1998 Optical Society of America
(120.6780) Instrumentation, measurement, and metrology : Temperature
(120.7250) Instrumentation, measurement, and metrology : Velocimetry
(300.1030) Spectroscopy : Absorption
(300.6210) Spectroscopy : Spectroscopy, atomic
(300.6260) Spectroscopy : Spectroscopy, diode lasers
Ole Trinks and Walter H. Beck, "Application of a Diode-Laser Absorption Technique With the D2 Transition of Atomic Rb for Hypersonic Flow-Field Measurements," Appl. Opt. 37, 7070-7075 (1998)