DETECTION OF $SiH_{4}-H_{2}O$ BY FOURIER TRANSFORM MICROWAVE SPECTROSCOPY

$^{a}$R.D. Suenram, G.T. Fraser, F.J Lovas, and Y Kawshima. J. Chem. Phys.101, 7230 (1994) $^{b}$Y. Ohshima, and Y. Endo, J. Chem. Phys., 93, 6256 (1990) $^{c}$Y. Kawashima, R. D .Suenram, G.T. Fraser, F.J. Lovas, and Y. Hirota. $51^{st}$ Symposium on Molecular specroscopy, (1996) TDO8Author Institution: Department of Applied Chemistry, Kanagawa Institute of Technology; Optical Technology Division, National institute of Standards and Technology; Optical Technology Division, The Graduate University of Advanced StudiesThe microwave spectra of the normal species, $^{29}Si, ^{30}Si, ^{18}O$, and $^{2}H SiH_{4}-H_{2}O$ 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 $SiH_{4}-H_{2}O$ were different from those of $CH_{4}-H_{2}O_{a}, CH_{4}-HCI_{b}$, and $Ar-SiH_{4}^{c}$. 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 $CH_{4}-H_{2}O(3. 70\AA)$.The value of the stretching force constant estimated For $SiH_{4}-H_{2}O$ from the rotational and centrifugal distortion constants is Larger than that for the C-O bond in $CH_{4}i-H_{2}O$. We thus Conclude the that Si-O bond in $SiH_{4}-H_{2}O$ is much stronger than the C-O bond in $CH_{4}-H_{2}O$. From the observed. Stark effect in $SiH_{4}-H_{2}O$, 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 $C_{2}$ axis coinciding with the van der Waals bond