15min:

PETER GRONER, Department of Chemistry, University of Missouri - Kansas City, Kansas City, MO 64110.

An effective rotation-internal motion Hamiltonian for molecules with two periodic internal motions has been applied recently to dimethyl ether and acetone whose equilibrium structures have C_2v symmetry. The program used to analyze their rotational spectra has been modified to allow treatment of two-rotor molecules with lower symmetry (equivalent rotor problems for molecules with C_s and C₂ symmetry and nonequivalent rotor problems with and without a plane of symmetry). It has been used to analyze the microwave literature data of CH₃SSCH₃ (C₂ symmetry, ground state) , CH₃CHFCH₃ (C_s symmetry, ground and two excited states) , and CH₃OSiH₃ (nonequivalent, C_s symmetry, ground state) . The experimental data have been fitted to experimental precision by the nonlinear least-squares method to determine spectroscopic parameters (rotational constants, centrifugal distortion constants and tunneling parameters). Applications to other molecules are in progress.