Gated integrators

Hz repetition rate of the lasers and is usually sampled with a gated integrator, whose output is reeorded with a laboratory eomputer. Analogue, rather than digital, eleetronies is usually employed beeause of pile-up of the deteeted photon eounts in an experiment with reasonable produet intensities. 

Jlidat N, Hliwa M, Joachim C (2008) A semi-classical XOR logic gate integrated in a single molecule. Chem Phys Lett 451(4—6) 270-275... 

Figure 9.12 Experimental setup (Nd YAG) Nd YAG laser (1064 nm, 50 Hz, 8 ns), (S) sample, (P) polarizer, (A) analyzer, (WP) waveplate (half or quarter rotated by steppermotor), (VF) visible-light-blocking filter, (PD) photodiode, (PMT) photomultiplier tube, (IRF) infrared filter, (IF) 532 nm interference filter, (PC) PC for data recording and control of the setup, (BC) boxcar/gated integrator, solid (dotted) line represents light at 1064 nm (532 nm).

The experimental set-up for femtosecond hyper-Rayleigh scattering is in essence identical to the one for the nanosecond experiments.9 Only the gated integrators for the nanosecond measurements are replaced by a chopper and a phase-sensitive detector in the high-frequency femtosecond experiment. 

Solutions were flowed through a suprasil flat cell (0.1 mm thickness) at rates between 0.1 - S.O mL/min in order to minimize any interference from signals produced by secondary photolysis of products. Time-resolved polarization evolution profiles for the formation and relaxation of the polarized radicals were measured at a constant magnetic field and monitored by both a Hitachi 40 MHz digital oscilloscope and a Stanford Research Systems gated integrator/boxcar averager at 5 ns resolution, and both coupled to a 486 PC desk-top microcomputer for analysis. 

Simultaneously with the ionization signals we monitored fluorescence signals. Gated integrators processed both these signals. We observed ionization signals with the laser tuned to... 

Fig. 2. Typical third-harmonic generation measurement. The beams from the laser source (here either a frequency shifted Nd YAG or a HoTmCnYAG laser) are split into a measurement and a reference beam. The polarization rotator and the polarizer serve as variable attenuator and yield the desired polarization of the input beam. The beam is focused on the sample in the vacuum chamber. The water filter removes the fundamental frequency and the attenuation filters limit the third-harmonic signal to the measurement range of the photomultiplier. The signal from the sample is divided by the reference signal and averaged with a boxcar gated integrator...

Fig. 1.13. Comparison between integrated continuous light-induced (upper trace) and time-resolved pulsed laser-induced (lower trace) EPR spectra from 45A Ti02 (0.3M) modified with ascorbic acid (0.08 M). The lower trace was obtained with a 550 nm laser (laser intensity 10 mJ per pulse, 10 ns pulse duration, 20 scans), 1 (is after the laser pulse. Both spectra were recorded at 8 K. Insert schematic presentation of events in time-resolved direct detection. The spectrum is taken at the time x after the laser pulse for each magnetic field using gate integrators. Magnetic field (H) is not modulated.

The transient recorder can be used as a digital oscilloscope for instrument tuning and diagnostics, as a gated integrator for ESEEM studies and as a transient recorder for FT-EPR. The maximum repetition rate is often limited by the TWTA duty cycle, but it is routine to operate the instrument at 1 2 kHz repetition rates. 

Feist H, Koep M, Reich H. (1971) A current transformer and gated integrator for measurement of week currents from pulsed accelerators. Nud Instr and Meth 97 319-321. 

Excitation and detection geometry, filter selection and electronic settings of the PMT/gated integrator are kept the same as in the LIF measurements. For absolute calibrations, the iZi(9) and /Zi(12) transitions of CH at 387.42 and 388.15 nm were selected [see Fig. 7(a)]. The CN calibration was performed using the Pi 2(10) transition at 388.11 nm. For the determination of concentration profiles of CH, the Ri(9) line was used. For CN, relative LIF intensity profiles talmn from transitions of the unresolved P(0,0)-bandhead at 388.44 nm were compared with profiles taken with the Pi 2(10) line. This comparison showed no difference within the error limits and therefore the bandhead was chosen in order to obtain a better signal to noise ratio. 

In a classical HRS experiment a ns pulsed laser (often Nd° YAG laser with a fundamental lightbeam of 1064 nm) is used. Because of the low repetition rate of the laser pulses, gated integrators are used to measure the intensity of the HRS signal. The measurement is computer controlled and and 4. are recorded. 

Fig. 2. Plot of the relative proportionality constant a as a function of the saturation (65,536 counts). Each data point represents at least 10 photoelectrons thus the uncertainty due to Poisson statistics is 10 . The data rvere accumulated using a very stable incandescent lamp and various accurately gated integration times. Plot (a) is the result of 42 tests of 5 different diodes across the array. In each test, the number of counts for a given exposure was compared with the number of counts recorded for a reference exposure corresponding to approximately 50% of saturation. The a value drops suddenly beyond 96% saturation. Plot (6) depicts the same data as (a) on an expanded scale in order to show the rapid dropoff of a as the percent of satination exceeds 96%. (Reprinted with permission from Menningen etal., 1995a, Contrib. Plasma Phys. 35, 359, 1995 Wiley-VCH, Inc.)...

The block diagram of the electronic circuitry is presented in Fig.2 the cathodically pulsed potential (Fig.3a) for the electroluminescence generation was provided by a microprocessor-based pulse generator with a home-made potentiostat (single operational amplifier (741) with a transistor booster) photomultiplier output was amplified, demodulated by a simple gated integrator and finally registered on a recorder. 

Figure 5 Schematic SHG setup. Key BS = beamsplitter. J2 = half-wave plate, P = polarizer, L = lens, F = filter, MC = monochromator, PMT = photomultiplier tube, Gl = gated integrator, DA = data acquisition, PD = photodiodes). (Reprinted with permission from Marrucci L, Paparo D, Cerrone G, et al. (2002) Optics and Lasers in Engineering 37 601-610. 2002, with permission from Elsevier.). The cell generally uses a reflection cell similar to that in Figure 2 with a Dove prism (Figure 4A (middle)).

Experimentally the UV sources are provided by two dye lasers giving a minimum of 2 x 250 pJ UV-light of 10 ns pulse duration in the range 260 - 285 nm. The benzene pressure was between 10 pbar and 200 pbar. The electrodes were biased with 16 V and the ion current following laser irradiation was collected by a gated integrator. Details can be found in Fig. 3. In thi way a complete ionization spectrum for several selected intermediate ( vibronic levels could be recorded fjom slightly ne-... 

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