Measurement of energetic electrons from atomic clusters irradiated by intense femtosecond laser pulses

Abstract

Spectra of energetic electrons in the 100 keV range were measured from the interaction of intense femtosecond laser pulses with clusters of xenon or argon. The interaction of 28 fs pulses with cluster targets revealed quite different results with respect to applied laser intensity. At the laser intensity of 1×1016 W/cm2, the absorption by xenon clusters was about 25%; however, at the laser intensity of 1×1017 W/cm2, the laser energy absorption drastically increased to 78%, and the efficient coupling between the laser pulse and cluster target produced electrons with energy as high as 500 keV. The estimated hot electron temperatures ranged from about 30 to 90 keV depending on atoms and backing pressures.

Laser-cluster interaction with subcycle pulses

“…With the cluster size being much smaller than the wavelength λ (usually 248-1064 nm), the laser radiation can efficiently couple to the solidlike atomic density with negligible skin-layer reflection and without hot electrons escaping into a cold bulk. Because of these advantages nearly 90% of laser energy can be absorbed [1] in clusters, producing ions of near MeV energies [1][2][3][4][5][6][7][8], electrons with keV energies [9][10][11][12][13], harmonic radiation [14][15][16][17][18], and x rays [19][20][21][22]. Nuclear fusion was also demonstrated with laser-heated deuterium clusters [23].…”

Influence of excitation and deexcitation processes on the dynamics of laser-excited argon clusters

“…The tem poral as evolution o f the cluster radius R is given as [37,49] W. (Z) coll -1t M d^P / ( P) -CT-on\ p e). (8) d R _ 5 (9) in w hich pm" = -J2meIz, and we substituted ip -cot. (14) by m eans o f the Fermi integral /3/2U ).…”

“…Starting with lasers op erating in the infrared (IR) regim e, characteristic features occurring in the laser-cluster interaction have been observed such as x-ray em ission [1,2] and the generation o f highorder harm onics [3,4], highly charged ions [5,6], and ener getic electrons [7][8][9]. Resulting from the progress in laser technology, the extensive investigation o f the laser-cluster interaction w ith IR laser fields [10][11][12] was later extended to laser radiation in the ultraviolet regim e [13,14], and it is now adays possible to perform experim ents even w ith x-ray photons [15,16] due to the advent o f free electron lasers.…”

Soft x-ray emission, angular distribution of hot electrons, and absorption studies of argon clusters in intense laser pulses

“…The generated hot electrons have strong influence on x-ray emission and enhance the x-ray emission. 15,16 The interactions of femtosecond laser pulses with clusters have some specific features characterized by the near solid density of a single cluster consisting of several hundreds, up to millions of atoms confined in a nanometer-sized volume. When a nanometer-sized cluster is heated by a femtosecond laser pulse, the electron density of the nanoplasma first rises to a supercritical level due to field ionization and collisional ionization, then decreases to a subcritical level because of nanoplasma expansion.…”