Spectrometer dispersive spectral apparatus

The possibilities of molecular beam spectroscopy can be enhanced by allowing for spectrally resolved fluorescence detection or for resonant two-photon ionization in combination with a mass spectrometer. Such a molecular beam apparatus is shown in Fig. 4.5. The photomultiplier PMl monitors the total fluorescence /r(A.l) as a function of the laser wavelength Xl (excitation spectrum. Sect. 1.3). Photomultiplier PM2 records the dispersed fluorescence spectrum excited at a fixed laser... 

Spectrometers are used to produce the spectrum or to isolate narrow spectral ranges, without further deconvolution. In dispersive apparatus, the spectrum is produced with a prism or diffraction grating. In nondispersive apparatus, spectral regions are isolated from the radiation beam by reflection, interference, or absorption in interferometers or filter monochromators. The latter are of use only in flame emission spectrometry. 

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