Reference PMT

Ratio-Referencing Spectrofluorometer A typical ratio-referencing spectrofluorometer is illustrated in Figure 3-20. Basically, this is a simple right angle instrument that uses two monochromators (Ml and M2), two photomultiplier tube detectors (D1 and D2, the reference and sample PMTs), and a xenon lamp source. The light from the exciter monochromator (Ml) is split, and a small portion (10%) is directed to the reference PMT (Dl) for ratio refer-... 

Figure 11.9 Schematic of a Shimadzu F-4500 spectrofluorometer. A fraction of the incident beam, reflected by a semi-transparent mbror, reaches a reference PMT. A comparison of the signals from the two PMTs leads to the elimination of any drifting of the source. This procedure, for single beam instruments, gives approximately the same stability as with a double beam spectrometer. However, the spectrum of a given solution will often present minor differences when recorded upon different instruments (reproduced courtesy of Shimadzu).

In the second step is identified the scmtillation sector at 1/12 symmetry companng the signal of the two Pmts adjacent to the reference one If the event is not in the reference sector (1/12) a reflection by n angle around the axis passing through the central and reference Pmts is performed... 

Because the scattmer and sani are rmt observed at the same time, the phase difference and relative modulation cannot be measuied at the same time. Ihslead, all measure-moils are perfimned relative to the refeseoce PMT (Figure 5dt). One fint measures the phase shift between die scat-iercr and reference PMT. These signals are drifted by an... 

Fig. 3 Light path diagram of TLC Scanner 3.1, Lamp selector 2, entrance lens system 3, entrance sht 4, grating monochromator 5, mirror 6, 20 fixed-slit aperture disk 7, lens system positioned in accordance with the slit size selected (choices are 0.5-12 mm length and 0.025-1.2 mm width) 8, mirror 9, beam splitter 10, reference PMT 11, plate to be scanned 12, measuring PMT 13, photodiode (transmission).

Note Units used du-ougliout Pmt 11 are diose used in die references. No effort was made to provide consistent units. 

FIGURE 24.4 Master curves of the local segmental relaxation times for 1,4-polyisoprene (-y = 3.0) 1,2-polybutadiene (7=1.9) polyvinylmethylether (7 = 2.55) polyvinylacetate (7 = 2.6) polypropylene glycol (7 = 2.5) polyoxybutylene (7 = 2.8) poly(phenyl glycidyl ether)-co-formaldehyde (7 = 3.5) polymethylphe-nylsiloxane (7 = 5.6) poly[(o-cresyl glycidyl ether)-co-formaldehyde] (7 = 3.3) and polymethyltolylsiloxane (PMTS) (7 = 5.0) [15 and references therein]. Each symbol for a given material represents a different condition of T and P. 

Figure 6. Instrumental schematic for vacuum UV photofragmentation-laser induced fluorescence measurement of ammonia SHGC, second harmonic generation crystal SFMC, sum frequency mixing crystal BS, beam splitter BD, beam dump TP, turning prism CL, cylindrical lens R, reflector TD, trigger diode OSC, oscillator cell AMP, amplifier cell BE, beam expander G, grating OC, output coupler M, mirror BC, beam combiner L, lens A, aperture PD, photodiode SC, sample cell RC, reference cell FP, filter pack SAM.PMT, sample cell photomultiplier REF.PMT, reference cell photomultiplier PP, additional photomultiplier port EX, exhaust and CGI, calibration gas inlet to flow line. (Reproduced with permission from reference 15. Copyright 1990 Optical Society of America.)...

The data recorded as the laser frequency is scanned consists of the fluorscence signal from the PMT, a Doppler-free I2 spectrum and frequency markers from the etalon. The etalon provides a calibration of the frequency scan. The Doppler-free I2 spectra provides an absolute frequency reference used to correct for small laser frequency drifts, separator voltage drifts and to determine the absolute acceleration voltage of the separator for the Doppler shift corrections. We are thus able to record data over long periods of time, e.g. 3 hours, and maintain a reasonable resolution of 100 MHz. Some of the first online data recorded with this system is shown in Figure 2. The overall detection efficiency has been measured to be 1/1000, i.e. one detected photon per 1000 atoms, for the largest transition in the nuclear spin 1/2 isotopes. 

Note These data were taken with a Varian copper HCL operated at 10 mA. The Cu 324.7-nm transition was a factor of 2.9 more intense than the 585.249-nm Ne transition. The spectrum was taken with an IP28 photomultiplier tube (PMT). The relative intensities were not corrected for the instrumental/PMT response. These data were taken from Reference 2. 

One photomultiplier tube measured the total (broad-band, spectrally) bioluminescence, and it was used as reference to compare the signals through the various filters. All signal counting was preceded by the dark-current counts of the PMT, averaged for the subsequent signal count time, and subtracted. The net signal count when filters were used was also corrected for the total transmittance of each filter and for the quantum efficiency of the phototube see Appendix). 

Single, double, triple refer to dispersive spectrometer type, PMT (photomultiplier tube), and CCD (charge-coupled device) refer to the detector. 

Figure 8.38. Transient Raman intensity recorded with a PMT during the electrochemical oxidation of dopamine in 1 M HBr. Each point represents a 20 msec integration of photons arriving at either 1572 or 1539 cm. Solid curves are simulated for a mechanism involving bromination of electrogenerated orthoquinone (1572 cm ) to yield a monobromo orthoquinone (1539 cm ). Applied potential was returned to a reducing value at r = 0.55. (Adapted from Reference 33 with permission.)...

Figure 10.1. Spectra of neon bulb emission, expressed as Raman shift (in air) relative to 514.532 nm. Obtained with Spex 1402 double monochromator, RCA 31034 PMT. Indicated values were calculated from Reference 2.

Figure 12.9. Spectrum of acetonitrile obtained with an immersed 18-around-l probe after lowering both sample and probe into liquid nitrogen. Spex 1403 scanning/PMT spectrometer, 514.5 nm laser, about 10 min total acquisition time. (Adapted from Reference 5 with permission.)...

Figure 12.31. Spectra from apparatus of Figure 12.30, obtained with a scanning/PMT spectrometer. Gap in /i-carotene spectrum occurred when shutter was closed to avoid large solvent band. (Adapted from reference 32 with permission.)...

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