The resonant transformation of a Gaussian pulse of electromagnetic radiation into a Langmuir wave in an inhomogeneous plasma is studied. It is shown that if the pulse duration is smaller than the Langmuir wave (plasmon) lifetime, then substantial changes in the Langmuir field profile occur. Namely, the width of this profile becomes greater and its maximum is smaller compared to the correspondent values for the case of long pulses and the same value of the plasmon lifetime. This fact may be useful for experimental measurements of the electron collision frequency. Indirectly, the collision frequency can be obtained by measuring the intensity of the the second harmonic of the postpulse emission, the expression for which in terms of the Langmuir field is given in this Letter. The limits of validity of linear theory due to plasma profile distortion and wavebreaking are discussed.
ASJC Scopus subject areas
- Physics and Astronomy(all)