Nonlinear Absorption and Far-Infrared Generation Under the Excitation of Ammonia Molecules by Strong IR Radiation

Abstract

We have investigated the excitation of N14H3 molecules (the pressure is 10⁻² − 1 Torr) under the effect of pulse radiation of the CO₂-laser in a wide range of fluences (Φ = 10⁻³−10 J/cm²) and detunings of the laser frequency from the absorption lines of the vibrational-rotational transition of the ammonia band ν₂. It is shown that the efficient excitation of ammonia under the influence of nonresonance IR radiation is due to the power broadening. In this case the calculation, which employs no fitting parameters, describes the experimental results within experimental errors. It is shown that the abnormally high absorption of ammonia in the case of resonance pumping is associated with an intense FIR generation which leads to elimination of the rotational bottle neck under the excitation of molecules.