Knowledge Bank

The microwave spectra of the normal species, $\mathrm{<mrow\; data-mjx-texclass="ORD">29</mrow>}Si,30Si,18O$, and $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}HSiH4-H2O$ have been measured using a pulsed-nozzle Fourier transform microwave (FTMW) spectrometer. Two, four and five strong transition were observed for the $J=1\leftarrow 0,2\leftarrow 1$, and $3\leftarrow 2$ transitions, respectively in the 7 to 22 GHz region. Almost all of the observed lines consisted of two or three components. The spectral patterns observed for $SiH4-H2O$ were different from those of $CH4-H2Oa,CH4-HCIb$, and $Ar-SiH4c$. The observed line frequencies were fitted to the expression for the rotational spectrum of a linear molecule. The centrifugal distortion constant of the set appearing at lower frequencies than the K=0 transition is much smaller than those of other transitions. The rotational constants thus obtained, give an Si-0 bond length of 3.38A, which is much shorter than the C-O bond length in $CH4-H2O(3.70\backslash AA)$.The value of the stretching force constant estimated For $SiH4-H2O$ from the rotational and centrifugal distortion constants is Larger than that for the C-O bond in $CH4i-H2O$. We thus Conclude the that Si-O bond in $SiH4-H2O$ is much stronger than the C-O bond in $CH4-H2O$. From the observed. Stark effect in $SiH4-H2O$, The electric dipole moment was determined to be 1.730 Debye. The structural and dipole data indicates that the water moiety is located with its $C2$ axis coinciding with the van der Waals bond.