PULSED ACCELERATED-FLOW SPECTROMETER WITH POSITION-RESOLVED OBSERVATION

The title instrument (PAF-PRO) permits the progress of rapid reactions to be monitored at 128 positions along a 2 cm observation cell as rea ctants now down the cell. A decelerated push is used to give velocity changes from 21 to 2 m s(-1) during a time interval of 384 ms, Variati on of now velocity allows reaction rate constants to be resolved from the physical mixing process. The now system brings the reacting soluti ons together in a 10-jet radial mixer 0.32 cm before the mixture enter s the observation tube (0.203 cm width, 1.945 cm length). A masked cha rge-coupled device (CCD) is the array detector used to obtain transmit tance data as a function of position and velocity. The masked portion of the CCD serves as a dynamic memory buffer for fast data acquisition . Pseudo-first-order rate constants are measured from 200 to 12000 s(- 1). The instrument also is calibrated for second-order reactions (equa l concentrations) with initial half-lives of 0.3-1.5 ms. Applications of the PAF-PRO system for the study of fast multistep reactions are pr esented.