Defined electromagnetic spectrum

The electromagnetic spectrum is shown in Figure 5.1 and most common spectroscopic methods are shown in Table 5.2. The spectroscopic regions are not exactly defined slightly different boundaries are found in the literature. 

The increase in energy in a molecule that occurs when radiation is absorbed can be accommodated in the three ways already described. The range of energies involved is characteristic of each type of change and is associated with a well-defined region of the electromagnetic spectrum (Figure 2.3). 

Nanometer Unit of length commonly used to define wavelength of light, particularly in the ultraviolet and visible ranges of the electromagnetic spectrum. It equals 10 m or 10 pm or 10 A. 

We consider, now, the time development of a molecule, with the spectrum defined in Section XI-A, under the influence of an electromagnetic field. As before, we shall use the method of analysis employed by Bixon and Jortner6 in the theory of radiationless processes, rather than more elaborate methods of Chock, Jortner, and Rice.8 Because the methodology is similar to that described in an earlier section, we shall only sketch the procedure used. 

Students will define the waves in the electromagnetic spectrum in terms of their wavelengths and frequencies. 

Speed is defined as distance traveled in a period of time. All waves in the electromagnetic spectrum travel in a vacuum at the same speed, the speed of light. What is this speed ... 

The photochemically active region of the electromagnetic spectrum has been divided into five sub bands the vacuum-UV (VUV), UV-C, UV-B, UV-A and VIS (Fig. 3-8). The subdivision of the UV spectral domain is mainly due to phenomenological reasons (Fig. 3-9) that are related to physical, biological or medicinal effects. The UV-B region is usually defined between X of 280 nm and 315 nm (van-... 

To get an idea of the amount of photons (i.e. the photon flow Op) that are emitted by different lamps at defined wavelengths in the VUV or UV region of the electromagnetic spectrum several examples are collected in Tab. 4-3. Note, that the same amount of photons, which is produced per period by a lamp at shorter wavelength consumes more of the lamp power, i.e. the photon flow Op is directly proportional to the wavelength X (cf Tab. 3-4). For example, a LP mercury lamp emits 0.344 mol h photons at X of 253.7 nm (Tab. 4-3). This is equivalent to a spectral power of the lamp of 45 W at this wavelength. On the other hand, the same amount of 172 nm photons would correspond to a spectral power Pj of 66 W (cf Tab. 3-4). 

---