The merit of the Hadamard transform active long-path absorption spectrometer was demonstrated by laboratory experiments. The dependence of measurement errors on the codes for the modulation was investigated. The spectral resolution of a spectrometer system and the deformation of the spectrum were tested. The sensitivity of the NO3 measurement in the 660-nm region was estimated for a system using high intensity LEDs and a room temperature photodiode array. The effect of the ghost of the Hadamard transform due to the nonlinearity of the detector and a method to correct the ghost are discussed.
A calculation procedure for correcting self-absorption of the spectral line by using a simple source model is proposed to improve the sensitivity of laser microprobe analysis. A linear calibration curve with a large slope is obtained by this method. This method is found useful for improving the analysis precision of the laser microprobe analyser.
Combining a nanosecond ruby laser with an image sensor detector system and a microcomputer, a convenient laser photolysis system has been constructed and a transient absorption spectrum in a 400-nm scanning region (at a delay time from 2 μs to 1 ms) can be recorded by one or two laser shots at a given temperature ranging from 88 K up to room temperature. The spectral resolution is 2.4 nm, while the temporal resolution may be on the tenth of microseconds due to a limited pulse width of the probing light (FWHM=1.7 μs). This laser photolysis system is convenient for discrimination of small differences in absorption spectra of short-lived species. Also, the system gives a correct absorption spectrum in the spectral region where strong emissions due to the transient species are observable.