OBSERVATION OF THE INVERSE LAMB DIP FOR INFRARED-MICROWAVE TWO-PHOTON TRANSITION PROCESSES IN AMMONIA
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Date
1972
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Ohio State University
Abstract
Observation of the inverse Lamb dip for infrared-microwave two-photon transition processes in ammonia is reported. The near coincidences between the P(15) line of the $N_{2}O$ laser and the $\nu_{2}[^{q}Q_-(4,4)]$ transition in ${15}NH_{3} (\Delta \nu = \ +\ 314 \pm 2MHz)$, and that between the R(6) line of the $CO_{2}$ laser and the $\nu_{2}[^{q}Q_+(5,4)]$ transition in $^{14}NH_{3}(\Delta \nu = + 558 \pm 2MHz)$ are made use of in these experiments. Frequency tunable microwave radiation is ``added’’ to fixed laser frequencies. In the two reported transitions, the Lamb dip is sufficiently strong to be observed on an oscilloscope with a short detector time constant (3 msec). The observations establish a method of measuring differences between laser frequencies and molecular absorption frequencies with high accuracy, even if the absorption is outside of the tuning range of the laser lines. A double resonance experiment involving the two-photon inverse Lamb dip is also discussed. Here a coherency splitting of the two-photon inverse Lamb dip is observed.
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Author Institution: Division of Physics, National Research Council of Canada