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Methods of absolute structure determination for molecules containing only light atoms (C, H, N, 0) are discussed in the paper. This experimentally difficult problem has a direct application in the structure determination of naturally originated compounds and modern chiral drugs. Several experimental methods of absolute structure determination like electron diffraction, multiple X-ray diffraction and X-ray anomalous scattering techniques are briefly discussed and compared. An application of dedicated azimuthal scan method for the case of hexamethylenetetramine is given as an illustration of this technique.

A new effective Hamiltonian is presented for the analysis of the high-resolution spectra of open-shell van der Waals complexes containing the O2 molecule. The effects of electron spin are included but the complications of nuclear spin and resultant nuclear spin splitting are neglected. The Hamiltonian is composed of the rotational, centrifugal distortion, and spin-spin interaction terms. The resulting energy levels are divided into two well-separated groups and the pattern is a complicated function of θ (the angle that the O2 molecule makes with the principal a axis of the complex) and φ (the azimuthal angle of the O2 out of the plane defined by the a and b axes of the complex). This model has been successfully applied to analyze the high-resolution spectrum of O2-N2O in the region of the N2O monomer ν3 vibrational band, which will be presented in a separate paper. © 1997 American Institute of Physics.

Recently, we have proposed a spin quantum cross structure (SQCS) device toward the realization of novel switching devices. The SQCS device consists of two ferromagnetic metal thin films with their edges facing each other at an angle of θ, and sandwiches a few molecules and atoms. In this paper, the calculation of electronic transport has been performed for SQCS devices with the Ni noncollinear magnetic films as both electrodes within the framework of the Anderson Hamiltonian, taking into consideration both polar angle θ, and azimuthal angle ϕ. We have obtained the general noncollinear spin transport formula, and the polar angle dependence of current-voltage characteristics of SQCS devices. The noncollinear spin transport is determined only by the angle θ defined by the inner product of two spins. Also, it is implied that SQCS devices can serve as multivalued memory devices by varying the angle θ.