xuv spectra of optical-field-ionized plasmas

Abstract

High-power Ti:sapphire laser pulses (150 mJ in 150 fs) were focused into a gas jet of He, N2, CQ2, 02, SF6, or Ar emitted from a pulsed nozzle. The xuv spectra that were generated are reported and analyzed. For all gases the spectra show strong lines corresponding to single-electron transitions. This indicates that the applied intensities of up to 5 X 10' %/cm' readily strip the atoms of all outer electrons, with three-body recombination populating excited levels of the next lower ionization stage. Simulations of the plasma evolution after the laser pulse were performed for helium and nitrogen. In the case of helium, good agreement with the experiment can be obtained for specific initial conditions. For nitrogen, mechanisms other than three-body recombination must be invoked to explain the experimental spectra. Gain measurements were made by comparing longitudinal and transverse spectra.

Saturated Amplification of a Collisionally Pumped Optical-Field-Ionization Soft X-Ray Laser at 41.8 nm

“…In spite of subsequent improvements [4] and numerous other investigations [5][6][7], the gain-length product in that scheme has never exceeded 10. Another breakthrough was the demonstration of a gain-length product of 11 in the collisionally pumped 5d-5p emission line at 41.8 nm of Xe 81 , by focusing a 70-mJ, 40-fs circularly polarized laser pulse into a gas cell filled with xenon [8].…”

Picosecond imaging of low-density plasmas by electron deflectometry

“…Owing to their unique properties, OFI plasmas have gained applications in various fields, such as inertial confinement fusion [1], generation of high-energy ions [2,3], x-ray emission [4,5], and x-ray lasers [6][7][8][9][10]. The parameters of OFI plasmas can be determined by a variety of diagnostic methods.…”

“…The electron temperature can be measured by Thomson scattering [11]. The ionization stage can be determined by ion spectrometry [12] and by x-ray spectroscopy [4]. The time-resolved plasma-density profile has been measured using optical interferometry, holography, and Moiré deflectometry [13][14][15].…”

<title>Collisional optical-field ionization soft x-ray lasers</title>

“…An OFT soft x-ray laser was first demonstrated in 1993 [3] with a recombination scheme on the Lyman a transition of Hlike Li. In spite of subsequent improvements [4] and numerous other investigations [5][6][7], the gain-length product in that scheme has never exceeded 10. Another breakthrough was the demonstration of a gain-length product of 1 1 in the collisionally pumped 5d-5p emission line at 41 .8 inn of Xe8, by focussing a 70 mJ, 40 fs circularly polarized laser pulse into a gas cell filled with xenon [8].…”