Ponderomotive energy

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In strong-field laser physics, ponderomotive energy is the cycle-averaged quiver energy of a free electron in an electromagnetic field. [1]

Contents

Equation

The ponderomotive energy is given by

,

where is the electron charge, is the linearly polarised electric field amplitude, is the laser carrier frequency and is the electron mass.

In terms of the laser intensity , using , it reads less simply:

,

where is the vacuum permittivity.

For typical orders of magnitudes involved in laser physics, this becomes:

, [2]

where the laser wavelength is , and is the speed of light. The units are electronvolts (eV), watts (W), centimeters (cm) and micrometers (μm).

Atomic units

In atomic units, , , where . If one uses the atomic unit of electric field, [3] then the ponderomotive energy is just

Derivation

The formula for the ponderomotive energy can be easily derived. A free particle of charge interacts with an electric field . The force on the charged particle is

.

The acceleration of the particle is

.

Because the electron executes harmonic motion, the particle's position is

.

For a particle experiencing harmonic motion, the time-averaged energy is

.

In laser physics, this is called the ponderomotive energy .

See also

References and notes


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