SPLITTING OF THE $ K = 3 $ ENERGY LEVELS OF THE GROUND STATE OF $AsH_{3}$
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Date
1973
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Ohio State University
Abstract
A splitting of the ground state K $= 3$ levels has been observed in the $\nu_{3}$ infrared band of $AsH_{3}$ at high J. The splitting follows the expected equation: $$\Delta_{3}=A[J^{3}(J+1)^{3}-8J^{2}(J+1)^{2}+12 J(J+1)]$$ with $A = 115$ Hz. This splitting constant is somewhat larger than the 86 Hz observed for $PH_{3}.^{1}$ The magnitudes of the observed splitting constants in $PH_{3}$ and $AsH_{3}$ can be explained by consideration of the effect of a term in the centrifugal distortion energy which is non-diagonal in the K quantum number. The centrifugal distortion contribution to the splitting constant is $2(\tau_{xxxz})^{2}/(C-B)$. From a normal coordinate treatment of $PH_{3}$ and $AsH_{3}$ this contribution to the splitting constant is calculated to be 110 Hz and 91 Hz for $PH_{3}$ and $AsH_{3}$, respectively, and the $A^{+}$ levels ($A_{1}$ for J even and $A_{2}$ for J odd) should lie below the $A^{-}$ levels ($A_{2}$ for J even and $A_{1}$ for J odd), as is observed for both molecules. $^{1}$P.B. Davies, R. M. Neumann, S. C. Wofsy, and W. Klemperer, J. Chem. Phys. 55, 3564 (1971).
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Author Institution: National Bureau of Standards