Single-channel spectrometer

As discussed in Section 3.4 and Chapter 4, the total acquisition time (Ia/) for a single-channel spectrometer is the integration time, ts, times the number of resolution elements. Operation at higher resolution will require more data... 

In automatic single-channel spectrometers, the angular positions 20a> 20b5 > at which lines Aa, Ab,. .. will be reflected, are preset the counter moves rapidly to position 20a remains there long enough to make an accurate intensity measurement, swings rapidly to 20b, etc. After each measurement the total counts received... 

Photomultipliers are used as detectors in the single-channel instruments. GaAs cathode tubes give a flat frequency response over the visible spectrum to 800 nm in the near IR. Contemporary Raman spectrometers use computers for instrument control, and data collection and storage, and permit versatile displays. 

The proton experiment is a so-called single channel experiment the same channel is used for sample irradiation and observation of the signal, and the irradiation frequency is set (automatically) to the resonance frequency of the protons at the magnetic field strength used by the spectrometer. 

Single beam, single channel type spectrometers... 

As with VCD, the first ROA instruments were built around single-channel scanning dispersive spectrometers [18,19,76,77], Photomultipliers with dualchannel photon-counting electronics were used to record the spectra. Scanning rates were no faster than 1 cm l per minute because of the requirement to accumulate at least 10 7 counts per spectral location, and preferably 10 . Applications with these instruments were limited to samples with favorable Raman scattering and the goals of these early studies were simply to explore the nature of ROA spectra and to improve measurement techniques. Several reviews... 

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