The energy level diagram of the Kr²⁶⁺ 3s → 2p transition array illustrating the two transitions at λ₁  7.504 Å and λ₂  7.265 Å

Figure 4. The energy level diagram of the Kr²⁶⁺ 3s → 2p transition array illustrating the two transitions at λ₁  7.504 Å and λ₂  7.265 Å. The corresponding spontaneous emission transition rates are also shown.

Abstract

Experimental evidence demonstrating amplification on the Kr²⁶⁺ 3s→2p transition at λ 7.5 Å (~1652 eV) generated from a (Kr)_n cluster medium in a self-trapped plasma channel produced with 248 nm femtosecond pulses is presented. The x-ray beam produced had a spectral width of ~3 eV and a corresponding beam diameter of ~150 µm, properties that were simultaneously determined by a two-dimensional x-ray spectral image formed with an axially placed von Hámos spectrometer and a matching Thomson image of the spatial electron density generated by the x-ray propagation.