Influence of a plasma medium on laser assisted radiative recombination

Abstract

The problem of laser assisted radiation recombination, taking into account the influence of the plasma in which the elementary process takes place, is investigated theoretically. Among the reported results, remarkable broadening and enhancement of the X-ray photon emission spectrum is found, provided some conditions are met. First, a sufficiently intense laser field must assist the process. For enhancement, the intensity must be such that the amplitude of the quiver electron velocity be comparable or slightly larger than the electron thermal velocity. For broadening it is important that at the level of the elementary act of recombination several multiphoton channels be open. A judicious compromise between the plasma temperature and the field intensity is necessary to have many effective slow electrons able to absorb large numbers of photons from the assisting laser field to be converted into X-ray photons. Emitted power spectra per steradian and frequency unit of the emitted photon J(ω x ) in a.u. as a function ω x for a Maxwellian EDF, ion charge Z=3, ω L =0.057 a.u., laser intensity I L = 6×10 15 W/cm 2 , different values of plasma temperature: dotted line T =1a.u. and R=7.3; thick line T=1,5 a.u. and R=5.9; thin line T= 2 a.u. and R=5.1

Asymmetries in the momentum distributions of electrons stripped by a XUV chirped pulse in the presence of a laser field

“…In the stimulated resonant radiative recombination the laser field is weak and only one-photon process occurs. The availability of intense laser fields allows to observe multiphoton processes in radiative recombination and it has prompted investigations i) in the regime of moderate intense fields, when more than one photon is exchanged, but the number of exchanged photons remains still small [10,11]; and ii) in the strong field regime, when a large number of photons participates to the process [12][13][14][15][16][17][18][19].…”

Control of multiphoton radiative recombination through the action of two low-frequency fields

“…In the last years particular attention has been paid to the laser assisted radiative recombination (LARR),as it may be considered an interesting process for the generation of high-frequency photons [1][2][3][4][5][6][7]. In the strong field context for the case of a single frequency, the main results may be summarized as follows: i) according to the energy conservation law, the energy of the emitted radiation is given (in atomic units) by…”

“…In the last years particular attention has been paid to the laser assisted radiative recombination (LARR),as it may be considered an interesting process for the generation of high-frequency photons [1][2][3][4][5][6][7].…”

“…( 1), in the presence of a laser field the radiation spectrum becomes richer as compared to the field free case, and n and ∆ are the sources of spectrum enlargement, shift to higher frequencies , and downward threshold shift as well. ii) The power spectrum exhibits larger values when many laser photons are absorbed, so that the presence of a laser field makes more probable the emission of photons with energy higher than that possible in the field free process [7]. iii) Strong enhancement of the total emitted power (TEP) summed over the channels of photons exchanged and integrated over all the directions of the incoming electron is found when the electron average translation velocity V q = (2ε q ) 1/2 is comparable to the amplitude of the quiver velocity V E = E 0L /ω L [6].…”

Controlling laser assisted radiative recombination with few-cycle laser pulses

“…of the external electromagnetic field. When the recombination process occurs in a very intense nonresonant monochromatic laser fields, a large number of photons may take part into the process, and many different multiphoton channels have comparable probabilities of occurrence [1][2][3][4][5][6][7][8][9].…”