Studies on Strongly Coupled Molecular Systems

Structure and dynamics of molecules，which are coupled each other by strong interactions of primarily ionic character，have been studied in detail experimentally and theoretically.Three types of molecular complexes have been investigated mainly by Fourier transform microwave spectroscopy：MOH(M=Na，K，Rb，and Cs)，MBH_4(M=Li，Na，and K)，and LiNaF_2.A characteristic feature of the molecular structure of the second group is that the M-B distance shows a quite large H/D isotopic effect，namely the distance decreases by 0.008to0.009A when H is reaced by D.This“the distance decreases by 0.008to0.009A when H is reaced by D.This”the distance decreases by 0.008to0.009A when His reaced by D.This sondy the bourier transform microwave spectroscopyThe x-y type Coriolis interaction was found to perturb the vibrational satellites of NaBH_4and KBH_4very much；the rotational spectrum of NaBH_4in the Na-B stretching state，for example，exhibits a K pattern which is reversed in frequency to that of the ground vibrational state。The perturbed satellites were analyzed by the least-…More squares method to yield the energy difference between the M-B stretching and the BH_4rocking states to be44.3and42.7厘米^&lt；-1&gt；for NaBH_4and KBH_4，respectively.The nuclear quadrupole coupling constants of Na and K in NaBH_4and KBH_4，which were measured，confirm that the M-(BH_4)bond is almost ionic.The boron nuclear quadrupole coupling constants in the two molecules are quite small，indicating that the BH_4structure closely approximates a tetrahedral structure.Theoretical studies were carried out on largeamplitude intramolecular motions in the methanol dimer and Na_3.A theory based upon group theoretical consideration was developed to facilitate the assignment of the K=0-0 transitions and of transitions involving the A K=1state，thereby allowing to interpret the observed splitting in terms of tunneling.Attention has been paid to pseudo-rotation expected to take place in the B state of Na_3.Again a theoretical treatment based on group theory was successfully applied to the analysis of the spectra of the B-X transition。Additional studies were performed on glycine and the SiH_4·Ar complex.The dipole moment was measured precisely for the two lowest-energy conformers of glycine in order to revise the energy difference between them to be705 cm^&lt；-1&gt；.The rotational transitions of SiH_4·Ar were found to consist of two K=0(A And F Symmetry)and three K=1(E And F Symmetry)compoents。The K=1，F lines were split by the internal rotation，and the analysis of these splittings yielded the barrier to internal rotation of about60厘米^&lt；-1&gt；.The Stark effect of the E lines led to the dipole monent of 0.027D.Less

Structure and dynamics of molecules, which are coupled each other by strong interactions of primarily ionic character, have been studied in detail experimentally and theoretically. Three types of molecular complexes have been investigated mainly by Fourier transform microwave spectroscopy : MOH (M=Na, K, Rb, and Cs), MBH_4 (M=Li, Na, and K), and LiNaF_2. A characteristic feature of the molecular structure of the second group is that the M-B distance shows a quite large H/D isotopic effect, namely the distance decreases by 0.008 to 0.009 A when H is replaced by D.This "secondary" isotope effect is ascribed mainly to the internal rotation of the BH_4 group. The x-y type Coriolis interaction was found to perturb the vibrational satellites of NaBH_4 and KBH_4 very much ; the rotational spectrum of NaBH_4 in the Na-B stretching state, for example, exhibits a K pattern which is reversed in frequency to that of the ground vibrational state. The perturbed satellites were analyzed by the least- … More squares method to yield the energy difference between the M-B stretching and the BH_4 rocking states to be 44.3 and 42.7 cm^<-1> for NaBH_4 and KBH_4, respectively. The nuclear quadrupole coupling constants of Na and K in NaBH_4 and KBH_4, which were measured, confirm that the M- (BH_4) bond is almost ionic. The boron nuclear quadrupole coupling constants in the two molecules are quite small, indicating that the BH_4 structure closely approximates a tetrahedral structure. Theoretical studies were carried out on largeamplitude intramolecular motions in the methanol dimer and Na_3. A theory based upon group theoretical consideration was developed to facilitate the assignment of the K=0-0 transitions and of transitions involving the A K=1 state, thereby allowing to interpret the observed splitting in terms of tunneling. Attention has been paid to pseudo-rotation expected to take place in the B state of Na_3. Again a theoretical treatment based on group theory was successfully applied to the analysis of the spectra of the B-X transition. Additional studies were performed on glycine and the SiH_4 ・ Ar complex. The dipole moment was measured precisely for the two lowest-energy conformers of glycine in order to revise the energy difference between them to be 705 cm^<-1>. The rotational transitions of SiH_4 ・ Ar were found to consist of two K=0 (A and F symmetry) and three K=1 (E and F symmetry) compoents. The K=1, F lines were split by the internal rotation, and the analysis of these splittings yielded the barrier to internal rotation of about 60 cm^<-1>. The Stark effect of the E lines led to the dipole monent of 0.027 D. Less