Wavelength terminology

Waveform can be defined in at least two different ways which are relevant to spectroscopic measurements. Wavelength (X.) is defined as the distance between successive peaks (Figure 2.1) and is measured in subunits of a metre, of which the most frequently used is the nanometre (10 9m). An angstrom unit (A) is not acceptable in SI terminology but is still occasionally encountered and is 10-10m (i.e. 10 A = 1 nm). The frequency of radiation (nu, v) is defined as the number of successive peaks passing a given point in 1 second. Hence the relationship between these two units of measurement is ... 

All types of electromagnetic radiation, or radiant energy, can be described in the terminology of waves. To help characterize any wave, we specify its wavelength (or its frequency). 

Artificial photonic crystals are structures built so that they contain diffracting centres separated by distances that are of the order of the wavelength of light. The interaction with light can be understood in terms of the Bragg equation. However, the terminology employed to describe diffraction in artificial photonic crystals is that of semiconductor physics. The transition from a diffraction description to a physical description can be illustrated with respect to a one-dimensional photonic crystal. 

Here A and B are constants, A the emission wavelength and Tc the temperature of the black body. With increasing Tc the color of the radiator moves ftom (infra)red into the visible. In luminescent lamp terminology, white is used for 35(K) K light, cool-white for 4500 K, and warm-white for 3000 K. 

At this point it is relevant to note the terminology employed in this chapter the expression laser-induced fluorescence (LIF) is used as a general term describing any fluorescence that is excited using a laser. A fluorescence excitation spectrum shows fluorescence emission yield as a function of excitation wavelength that is, it is similar to an absorption spectrum when that absorption results in radiative emission. It is noted that some authors reserve LIF as a synonym for fluorescence excitation spectroscopy. Dispersed fluorescence refers to dispersion of the emitted fluorescence light into its component wavelengths, that is, production of an emission spectrum. 

Where radiative relaxation takes place, each transition shown in Figure 2 induces the emission of radiation of specific wavelength/energy, characteristic for the atomic species involved. In Figure 2, the terminology adopted by Siegbahn for the characteristic X-ray lines is used, showing that in an iron... 

The study of wave behavior is a topic for another course, but we need some basic terminology to understand atoms. Waves have three basic characteristics wavelength, frequency, and speed. Wavelength (lambda. A) is the distance between consecutive peaks (or troughs) in a wave, as shown in Figure 10.1. Frequency (nu, v) tells how many waves pass a particular point per second. Speed (v) tells how fast a wave moves through space. 

The coefficients in the various terms in Eqs. (2a) and (2b) are termed the nth-order susceptibilities. The first-order susceptibilities describe the linear optical effects, while the remaining terms describe the nth order nonlinear optical effects. The coefficients are the nth-order electric dipole susceptibilities, the coefficients G " are the nth-order quadrupole susceptibilities, and so on. Similar terminology is used for the various magnetic susceptibilities. For most nonlinear optical interactions, the electric dipole susceptibilities are the dominant terms because the wavelength of the radiation is usually much longer than the scattering centers. These will be the ones considered primarily from now on. 

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