Collision-induced amplification of short-wave radiation on transitions to the ground state of atoms

A new version of obtaining short-wave lasing on transition between highly excited states and the ground state of active atoms in the buffer gas atmosphere is studied theoretically. The mechanism of obtaining population inversion on such a transition is associated with the establishment of the local Boltzmann distribution of populations in a group of highly excited levels due to frequent collisions. If the excitation of the upper-lying level is performed by two laser radiation sources with frequencies ω₁ and ω₂, short-wave lasing can be obtained at a frequency close to the total frequency ω₁ + ω₂. The conditions for the emergence of population inversion are analyzed and simple analytic formulas are derived. It is shown that collision-induced enhancement of short-wave radiation can occur for pumping intensities on the order of 100 W/cm². For pumping intensities on the order of 1000 W/cm², the amplification factor for short-wave radiation may attain values of 3 cm^?1 (for an active atom concentration of N ～ 10¹⁵ cm^?3), which is sufficient for the development of lasing per path through an active medium (superradiance condition) for a length of the active medium on the order of 10 cm.