Charge-exchange-induced formation of hollow atoms in high-intensity laser-produced plasmas

Abstract

For the first time registration of high-resolution soft x-ray emission and atomic data calculations of hollow-atom dielectronic satellite spectra of highly charged nitrogen have been performed. Double-electron charge-exchange processes from excited states are proposed for the formation of autoionizing levels in high-intensity laser-produced plasmas, when field-ionized ions penetrate into the residual gas. Good agreement is found between theory and experiment. Plasma spectroscopy with hollow ions is proposed and a temperature diagnostic for laser-produced plasmas in the long-lasting recombining regime is developed.

Diagnostics of warm dense matter by high-resolution X-ray spectroscopy of hollow ions

“…This effect was first discovered and explained by Rosmej et al (1999), which was dedicated to the experimental and theoretical investigation of intense femtosecond laser pulses with high-pressure nitrogen. The experiments of Rosmej et al (1999) were performed on the titaniumsapphire laser of the Saclay Research Center (France).…”

“…The experiments of Rosmej et al (1999) were performed on the titaniumsapphire laser of the Saclay Research Center (France). Laser pulses with a linear p-polarization were focused onto a pulsed nitrogen gas target.…”

“…8). Rosmej et al (1999) hypothesized that these structures arise from radiative transitions from the highly excited nln 0 l 0 states of hollow He-like nitrogen ions. Atomic calculations performed using the multi-configuration HartreeFock method with the inclusion of relativistic corrections for hollow configurations (3l5l 0 , 4l5l 0 , 5l5l 0 , 3l6l 0 , 4l6l 0 , 5l6l 0 , 6l6l 0 , 3l7l 0 , 4l7l 0 , 5l7l 0 , 6l7l 0 , 7l7l 0 , 3l8l 0 , 4l8l 0 , 5l8l 0 , 6l8l 0 , 7l8l 0 , and 8l8l 0 ) confirmed this assumption, at least for the wavelengths of the observed spectral peaks.…”

“…This signifies that, in this case, the hollow ion states for some reasons are anomalously densely populated in comparison with the singly excited states of hydrogen-like ions. To explain this anomalous behavior of level populations, Rosmej et al (1999) proposed a physical mechanism involving charge exchange in collisions of multi-charged and lowcharged nitrogen ions. The scenario of this mechanism is as follows.…”

“…We note, however, that N 2 molecules, even though far away from the central spot, may be destroyed by sufficiently high-energy particles (photons and electrons) generated in the central region. That is why, in accordance with Rosmej et al (1999), it will be assumed that the nuclei collide with N +0 , N +1 ‡ and N +2 ‡ ions, resulting in the following single-or double-electron charge-exchange reactions…”