In strong-field laser physics, ponderomotive energy is the cycle-averaged quiver energy of a free electron in an electromagnetic field. 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: , 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, 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 Ponderomotive force Electric constant Harmonic generation List of laser articles References and notes Laser science Energy (physics)