Data collection detector delay

Constraints such as the presence of a continuum background, line broadening and selfabsorption can be minimized by using time-resolved LIB spectroscopy (TRE-LIBS) 

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Laser-assisted solid sampling 9.3.8. Data collection detector delay... 

The time resolution of the instrument is governed not only by the pulse width but also by the electronics and the detector. The linear time response of the TAC is most critical for obtaining accurate fluorescence decays. The response is more linear when the time during which the TAC is in operation and unable to respond to another signal (dead time) is minimized. For this reason, it is better to collect the data in the reverse configuration the fluorescence pulse acts as the start pulse and the corresponding excitation pulse (delayed by an appropriate delay line) as the stop pulse. In this way, only a small fraction of start pulses result in stop pulses and the collection statistics are better. 

The second stage is data acquisition. This stage is entered when the operator starts the instrument. The instrument makes the first injection and signals the microcomputer via Intelink. After a delay proportional to the void volume of the column set, data are collected on a time basis (constant flow rate assumed) at the predetermined rate from each of the detectors selected, up to a maximum of three simultaneous detectors. VHien the sample run is complete, the instrument again signals the microcomputer which places the instrument in a hold state while it reads the operational parameters from the instrument for that sample and... 

Schematically, two main systems can be used to collect 3D fluorescence data (time, wavelength, number of photons, see fig. 1). In a first type of system, light is directed into a monochromator connected to a photomultiplier tube and then to a fast oscilloscope (PM detection). The experimentalist thus collects luminescence decays at various wavelengths. This system is known to be very efficient for luminescence decay acquisition but is very time-consuming for the acquisition of emission spectra. In the second type of system, light is directed to a diode array detector (or CCD camera) and a subsequent electronic detection device (diode detection). The experimentalist collects emission spectra at various delay times (time zero for the pulse entering in the sample). This system is very efficient for emission data acquisition but, on the other hand, time-consuming for luminescence decay acquisitions. From this very schematic description, it appears that a system combining the two types of detections would be the optimum.

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