Collisionless excitation of NH3 molecules via one- and two-photon transitions by multimode radiation of TEA CO2 laser

摘要

The excitation of ammonia via one- and two-photon transitions by TEA CO$-2$/- laser radiation has been studied under collisionless conditions. It has been shown that the experimental results of two-photon excitation of $+14$/NH$-3$/ molecule in the 2 $nu$-2$/ a(1, 1) $IMP a(1, 1) transition by the 10P(24) CO$- 2$/-laser line, the frequency offset of which is $APEQ 0.02 cm$+$MIN@1$/, can be described well by modeling the laser radiation as a broadband chaotic field. The experimental results of one-photon excitation in $+14$/NH$-3$/ and $+15$/NH$-3$/,$+4$/ with the offset values exceeding the CO$-2$/-laser linewidth, can be also described well with the use of a chaotic field with a continuous spectrum. In the case of a nearly exact one-photon resonance, however, the excitation efficiency of molecules depends critically on the real mode structure of the CO$-2$/-laser radiation.