Investigation of the inverted populations of the levels of OVII ions

An experimental investigation was made of the optical characteristics of a plasma formed as a result of irradiation of an Al₂O₃ target in vacuum by high-power neodymium laser radiation. A study was made of helium-like oxygen ions and it was established that a recombination mechanism of the population of the levels could give rise to a gain of ~10^–2 cm^–1 for the n = 4→n = 3 transition, where n is the principal quantum number.