Waves light

Spectroscopists observed that molecules dissolved in rigid matrices gave both short-lived and long-lived emissions which were called fluorescence and phosphorescence, respectively. In 1944, Lewis and Kasha [25] proposed that molecular phosphorescence came from a triplet state and was long-lived because of the well known spin selection rule AS = 0, i.e. interactions with a light wave or with the surroundings do not readily change the spin of the electrons. 

Spectral lines are fiirther broadened by collisions. To a first approximation, collisions can be drought of as just reducing the lifetime of the excited state. For example, collisions of molecules will connnonly change the rotational state. That will reduce the lifetime of a given state. Even if die state is not changed, the collision will cause a phase shift in the light wave being absorbed or emitted and that will have a similar effect. The line shapes of collisionally broadened lines are similar to the natural line shape of equation (B1.1.20) with a lifetime related to the mean time between collisions. The details will depend on the nature of the intemrolecular forces. We will not pursue the subject fiirther here. 

Up to this point, we have calculated the linear response of the medium, a polarization oscillating at the frequency m of the applied field. This polarization produces its own radiation field that interferes with the applied optical field. Two familiar effects result a change in tlie speed of the light wave and its attenuation as it propagates. These properties may be related directly to the linear susceptibility The index of... 

Bloembergen N and Pershan P S 1962 Light waves at the boundary of nonlinear media Rhys. Rev. 128 606-22... 

Now if we consider die atom moving in die +z direction widi velocity and counteriiropagating to die light wave detuned from resonance by Acuj, die net detuning will be... 

The phases studied in the present work are those of material, Schrodinger waves, rather than of electromagnetic, light waves. Recently, it has been shown... 

If we think in terms of the particulate nature of light (wave-particle duality), the number of particles of light or other electi omagnetic radiation (photons) in a unit of frequency space constitutes a number density. The blackbody radiation curve in Fig. 1-1, a plot of radiation energy density p on the vertical axis as a function of frequency v on the horizontal axis, is essentially a plot of the number densities of light particles in small intervals of frequency space. 

Valence bond and molecular orbital theory both incorporate the wave description of an atom s electrons into this picture of H2 but m somewhat different ways Both assume that electron waves behave like more familiar waves such as sound and light waves One important property of waves is called interference m physics Constructive interference occurs when two waves combine so as to reinforce each other (m phase) destructive interference occurs when they oppose each other (out of phase) (Figure 2 2) Recall from Section 1 1 that electron waves m atoms are characterized by their wave function which is the same as an orbital For an electron m the most stable state of a hydrogen atom for example this state is defined by the Is wave function and is often called the Is orbital The valence bond model bases the connection between two atoms on the overlap between half filled orbifals of fhe fwo afoms The molecular orbital model assembles a sef of molecular orbifals by combining fhe afomic orbifals of all of fhe atoms m fhe molecule... 

In this discussion we define the x direction to be the direction of propagation of the light waves. This means that the yz plane contains the oscillating electrical and magnetic fields which carry the energy of the radiation. Only the electric field concerns us in scattering. Since the oscillation is periodic in both time t and location x, the electric field can be represented by the equation... 

The time period A/ia which the light wave undergoes random changes is called the coherence time. It is related to the Hnewidth Av of the laser by the equation... 

A wide variety of other nonlinear optical effects also have been demonstrated. According to equation 12, if two light beams having frequency CO and CO2 are combined in a material with a nonzero value of light waves of frequency + UJ2 and are produced. A combination of such effects, used... 

The thickness of a film influences the interference of light waves reflected from the front and back of the film, and hence the reflectance. The thickness of an absorbing film can, therefore, be measured only as long as there is still a contribution of from the back of the film to the reflectance of the sample. Typical measurable thicknesses of metallic layers are <50 nm. 

Diffraction modification of the behavior of a light wave resulting from limitations of its lateral extent by an obstacle. For example, the bending of light into the "shadow area" behind a particle. 

UV Radiation Electromagnetic radiation in the wavelength range of approximately 4 X 10 to 5 X 10 m, i.e., between visible light waves and X-rays. 

What causes optical rotation The plane of polarization of a light wave undergoes a minute rotation when it encounters a chiral molecule. Enantiomeric forms of a chiral molecule cause a rotation of the plane of polarization in exactly equal fflnounts but in... 

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