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Studies on Strongly Coupled Molecular Systems

强耦合分子系统研究

基本信息

批准号：
05044045
负责人：
HIROTA Eizi
金额：
$ 6.4万
依托单位：
The Graduate University for Advanced Studies
依托单位国家：
日本
项目类别：
Grant-in-Aid for international Scientific Research
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1995
项目状态：
已结题

项目摘要

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

通过主要离子特性的强相互作用相互耦合的分子的结构和动力学已经在实验和理论上进行了详细研究。主要通过傅里叶变换微波光谱研究了三种类型的分子配合物：MOH（M=Na、K、Rb和Cs）、MBH_4（M=Li、Na和K）和LiNaF_2。第二组分子结构的一个特征是M-B距离表现出相当大的H/D同位素效应，即当H被D取代时距离减小0.008至0.009 A。这种“次级”同位素效应主要归因于BH_4基团的内旋转。发现x-y型科里奥利相互作用对NaBH_4和KBH_4的振动卫星有很大的扰动；例如，NaBH_4在Na-B伸缩态下的旋转谱表现出频率与基振动态频率相反的K模式。通过最小二乘法对扰动卫星进行分析，得到NaBH_4和KBH_4的M-B拉伸态和BH_4摇摆态之间的能量差分别为44.3和42.7 cm^<-1>。测量的NaBH_4和KBH_4中Na和K的核四极耦合常数证实M-(BH_4)键几乎是离子键。两个分子中的硼核四极耦合常数非常小，表明BH_4结构非常接近四面体结构。对甲醇二聚体和Na_3的大幅分子内运动进行了理论研究。开发了一种基于群理论考虑的理论，以促进 K=0-0 跃迁和涉及 A K=1 状态的跃迁的分配，从而允许根据隧道效应解释观察到的分裂。人们注意到 Na_3 的 B 态中预计会发生的赝旋转。基于群论的理论处理再次成功应用于 B-X 跃迁光谱的分析。对甘氨酸和 SiH_4·Ar 络合物进行了其他研究。精确测量甘氨酸的两个最低能量构象异构体的偶极矩，以便将它们之间的能量差修正为705cm ^ -1 。 SiH_4·Ar的旋转跃迁被发现由两个K=0（A和F对称）和三个K=1（E和F对称）分量组成。 K＝1，F线通过内旋转分裂，并且对这些分裂的分析产生约60cm 2 -1的内旋转势垒。 E 线的斯塔克效应导致偶极矩为 0.027 D。小于