For measurements of transient absorption a laser-raster technique has been found to be surprisingly sensitive. It utilizes spatial separation of excitation and probing by employing a fast-flowing jet stream. The time resolution is determined by the flow velocity and the focal diameters of the continuous excitation and probing laser beams. Changes in transmission can be detected in the spectral region from 350 to 1000 nm. A dual-frequency modulation technique is used to achieve a sensitivity of 10<sup>−4</sup>. The time resolution is 0.5 μs. The performance of this spectrometer is demonstrated by measurement of the absorption of the transient states of Rhodamine 6G dye in ethylene glycol.
© 1999 Optical Society of America
(300.6190) Spectroscopy : Spectrometers
(300.6360) Spectroscopy : Spectroscopy, laser
(300.6390) Spectroscopy : Spectroscopy, molecular
(300.6500) Spectroscopy : Spectroscopy, time-resolved
(300.6550) Spectroscopy : Spectroscopy, visible
Ingo Gregor and Erwin Thiel, "Laser-Raster Spectrometer for Time-Resolved Recording of Transient Absorption," Appl. Opt. 38, 7468-7474 (1999)