# MICROWAVE-MICROWAVE FOUR-LEVEL DOUBLE RESONANCE IN $NH_{3}$-He AND $NH_{3}-H_{2}$ GAS $MIXTURES^{\ast}$

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 Title: MICROWAVE-MICROWAVE FOUR-LEVEL DOUBLE RESONANCE IN $NH_{3}$-He AND $NH_{3}-H_{2}$ GAS $MIXTURES^{\ast}$ Creators: Peterson, D. B.; Schwendeman, R. H. Issue Date: 1984 Publisher: Ohio State University Abstract: Recently, Davis and $Green^{a}$ have reported the results of calculations of the four-level double resonance effect that occurs when the amplitude of the microwave absorption for a single transition in $NH_{3}$, in an excess of He, is monitored while the microwave power in resonance with a second $NH_{3}$ transition is increased to saturation. The recent calculations, which included specific consideration of the effects of the M degeneracy, were compared with the experimental results reported by $Oka^{b}$ and by Fabris and $Oka.^{c}$ As was the case for previous calculations by Davis and $Boggs,^{d}$ the more recent calculations show large discrepancies between observed and calculated values of the four-level effects, especially for the case in which the pump and signal transitions have the same k value. In order to reduce the possibility that the poor agreement between theory and experiment is the result of some systematic experimental error, we have repeated many of the experimental measurements performed in Oka's laboratory for both $NH_{3}$-He and $NH_{3}-H_{2}$ mixtures, and have extended the $NH_{3}-H_{2}$ data. Our measurements, which were performed with apparatus in our laboratory, are in very good agreement with those previously obtained. Description: $^{\ast}$This research was supported by the U. S. National Science Foundation. $^{a}$ S. L. Davis, and S. Green, J. Chem. Phys. 78, 2170 (1983). $^{b}$ T. Oka, J. Chem. Phys. 49, 3135 (1968). $^{c}$A. R. Fabris and T. Oka, J. Chem. Phys. 56, 3168 (1972). $^{d}$ S. L. Davis and J. E. Boggs, J. Chem. Phys. 69, 2355 (1978). Author Institution: Department of Chemistry, Michigan State University URI: http://hdl.handle.net/1811/16561 Other Identifiers: 1984-FA-2