Light transitions between energy

Fig. 1 The effect of size on metals. Whereas bulk metal and metal nanoparticles have a continuous band of energy levels, the limited number of atoms in metal clusters results in discrete energy levels, allowing interaction with light by electronic transitions between energy levels. Metal clusters bridge the gap between single atoms and nanoparticles. Even though in the figure the energy levels are denoted as singlets, we must remark that the spin state of the silver clusters is not yet firmly established...

For light to induce a transition between energy levels of an atom or molecule, it is necessary that the frequency of the hght and the energy difference between the levels satisfy, at least approximately, the Planck relationship ... 

Use the Bohr model to calculate the energy levels of one-electron atoms and to find the freqnencies and wavelengths of light emitted in transitions between energy levels (Section 4.3, Problems 19-22). 

The interaction of radiation with matter can cause redirection of the radiation or transitions between energy levels of the atoms and molecules, or both. More subtle effects involve not only the color or wavelength of the radiation but its change in intensity and in the polarization of the light. It is by spectroscopy that we are able to... 

How can light cause transitions between energy levels ... 

The energy levels of atoms and molecules can be studied experimentally by measuring the wavelengths of the light that is emitted, absorbed, or scattered in transitions between energy levels. According to the Planck-Einstein relation of Eq. (14.4-8), the energy of a photon is... 

Laser light is produced from transitions between atomic or molecular energy levels. Generation of light requires two energy levels, E and E separated by the photon energy E of the light that is to be produced. 

The nature of light absorption in a crystal is of no significance for theory. What is important here is that this absorption be photoelectrically active, i.e., results in a change of the concentration of free carriers in a crystal. This process may take the form either of the so-called intrinsic absorption accompanied by the transition of an electron from the valency to the conduction band, or of the so-called impurity absorption caused by an electronic transition between the energy band and the impurity local level. 

The model of metal-ammonia solutions that has emerged is based on ionization of the metal atoms to produce metal ions and electrons that are both solvated. The solvated electron is believed to reside in a cavity in ammonia, and thus it may behave as a particle in a three-dimensional box with quantized energy levels. Transitions between the energy levels may give rise to absorption of light and thereby cause the solutions to be colored. The dissolution process can be represented as... 

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