Forced oscillations, electromagnetic field

Infrared spectroscopy probes the characteristic vibrational bands of chemical groups as the atoms move with respect to one another in response to an oscillating electromagnetic field of the appropriate frequency. The normal modes of a particular molecule or group depend on the molecular structure, interatomic forces (bond strengths) and masses of the atoms concerned, but they will only be IR active if the vibrational mode involves a change in dipole moment. 

It is not heretical to consider the electromagnetic vacuum as a physical system. In fact, it manifests some physical properties and is responsible for a number of important effects. For example, the field amplitudes continue to oscillate in the vacuum state. These zero-point oscillations cause the spontaneous emission [1], the natural linebreadth [5], the Lamb shift [6], the Casimir force between conductors [7], and the quantum beats [8]. It is also possible to generate quantum states of electromagnetic field in which the amplitude fluctuations are reduced below the symmetric quantum limit of zero-point oscillations in one quadrature component [9]. 

Modern sensors are remarkable in many ways. Their small dimensions open up new areas of mechanics, flow control, friction, and oscillation. Force measurements are just one example. The once somewhat obscure classical Coriolis force is now the principle means of sensing rotation. And the even more obscure miniscale quantum-mechanical Casimir force, arising between two close interfaces, is now also accessible to sensor structures. Sensitivities are astonishing even now, but will most probably continue to be enhanced. Very many external parameters, such as temperature, pressure, and electromagnetic fields, can be accurately and quickly measured. What a wonderful area of activity for physicists, chemists, engineers - and salespeople alike The prospect of protecting humankind as well as the environment is gratifying. 

The physical basis of the Raman effect is related to deformation of electron shells of molecules in an electric field E determined by the molecular polarisability a. Because the laser beam can be considered an oscillating electromagnetic wave with the electrical vector E and a frequency v0 it induces during interaction with the sample the electric dipole momentum P = aE. This momentum is the driving force of the deformation of the electronic shells of the molecules. Because this deformation is periodical, the molecular dipoles begin to vibrate with a characteristic frequency vm. 

The hydrodynamic motion is considered to be the motion in the potential (elastic forces) and nonpotential (resistance forces) fields. There are several possible approaches to correlate the electromagnetic and mechanical oscillations for example, this motion may be represented by the differential equation for the forced oscillation ... 

In this section we discuss the interaction between an electric field and a charge that is free to move with the field. Such a charge experiences a force that accelerates it with the field. If the field is oscillating, the acceleration of the charge will also oscillate. One of the basic results of classical electromagnetics is that the acceleration of a charge leads to the emission of radiation. 

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