Electromagnetic mirror separation

A double beam instrument splits the electromagnetic radiation into two separate beams, one for the reagent blank, and the other for the sample. There are two ways to do this. The first method uses a mirror that is half silvered and half transparent. As shown in Fig. 5.17 this results in a continuous beam of light for both the sample and reagent blank. 

A spectroscope is an instrument used to disperse a beam of electromagnetic radiation into its component waves. Many spectroscopes have diffraction gratings that separate the waves, which are beamed to a mirror and reflected back to the eye of an observer. Each wave appears as a separate colored line. 

Fig. 11.8 Pulse sequence and field-matter interactions in a three-pulse photon-echo experiment. (A) Pulses 1, 2 and 3, traveling from right to left in this diagram, reach the sample with different wavevectors ki, k2 and kf). Pulses 1 and 2 are separated by time interval t pulses 2 and 3, by interval T. Photon echos with wavevectors kj, (Joi—kf) are measured. (B) Interactions of the sample with the electromagnetic fields wavy arrows) occur at times t-t2,-t2 t (sometime during pulse 1), t-t2,-t2 (during pulse 2), and t-t (during pulse 3), and the echo (P ) is emitted at time t. The signal is integrated from t3 = 0 to oo. Figure 11.13 shows how movable mirrors can be used to control the pulse timing in such experiments...

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