The classical pump-probe scheme for experiments with femtosecond laser is proposed to use for study the inequality of forward and reversed transitions in optics.
Theoretical and experimental study of nonresonance generation of laser radiation by atoms, molecules and ions of matter - superradiation - is an important area of research in the field of femtosecond optics. Narrowly directed (forward and reverse), with an intensity proportional to the square of the number of inverted atoms, molecules and ions, radiation can be used to probe the atmosphere using femtosecond lidars. This paper presents the results of comparative experimental studies of the appearance of superradiance at transitions of molecular nitrogen ion in the atmosphere and at transitions of atomic strontium ion in a mixture with inert gases (He, Ne) in a heated cuvette. For the first time, superradiance was observed in the transition from the resonant electronic state 2Р1/2 / to the ground state 2S1/2 (407.8 nm), when Sr pairs were pumped by radiation at a wavelength of 268.1 nm.