Evidence of population inversion in Li-like aluminum ions in a laser produced plasma

Soft X-ray emissions of a line-shaped aluminum laser produced plasma have shown anomalous intensity of an unknown line at 105.7 A. This line has been identified with the 3d-5f transition of Al(10 plus) ions. An experimental method for measuring the plasma absorption has been established. Absorption measurements show the evidence of a population inversion between 3d and 5f levels, which is corroborated by detailed calculations of the rate equations with a convenient plasma model.