Study of vib-rotational spectra of van der Waals complexes containing SH4 and CH4

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We have searched for rotational spectra of CD4--H20 and GeH4--H20 using a Fourier transform microwave (FTMW) machine which was built in our lab in 1998. Very recently we succeeded in observing the rotational spectra of CD4--H20, However, we could not detect a spectrum of GeH4--H20 and are still searching it. When a rotational spectrum of CH4--NO was searched, many absorption lines of trans- and cis-HONO and N2O3 were observed. Next we considered how to explain the difference between the spectral patterns of Ar--SiH4 and Ar--SiD4 which had already been observed using a FTMW spectrometer. It was difficult to explain the observed spectral patterns considering only a Coriolis interaction term, which couples the internal rotation of SiH4 and the end-over-end rotation of the complex. Then we considered an anisotropic potential of a van der Waals stretching mode for Ar--SiH4 and expanded this potential by a power series of van der Waals bond distance. In order to fit the observed spectral patterns of Ar--SiH4 and Ar-. SiD4, the potential orders were chosen to be -15 and -9, respectively. These values were corresponded to the repulsive and attractive forces of the Lennard-Jones potential for a spherical top molecule. In the addition, we tried to explain the observed rotational spectra of SiH4--H20 system by taking account for a diagonalization of the general internal rotation Hainiltonian. The potential barrier of SiH4--H20 was estimated to be about 260 cm- 1 because of rather strong hydrogen bonding. Finally, analyzing the rotational spectra of the excited vibrational states for LiBH4 and NaBH4, the energy differences and the Coriolis interaction constants were determined.