Calculations of molecular ir spectra in the overtone and combination frequency regions

Frequencies and intensities of fundamental, overtone, and combination absorption bands have been calculated in an anharmonic approximation for substituted benzene and ethene, aldehydes, ketones, and alcohols in the range 400–4000 cm^–1. The calculated values agree well with the experimental data. It is shown that such a calculation allows one to study and predict dependences of the frequencies and intensities of the overtone and combination bands on the substance structure.     

Variational method for the calculation of the vibrational structure of the electronic spectra of polyatomic molecules. I

A method is proposed to calculate the vibrational structures of the electronic spectra of polyatomic molecules based on the variational solution of the vibrational problem in the excited state with the vibrational wave functions of the ground state as basis set. The electrono-vibrational problem leads to an evaluated and diagonalized variational matrix. The elements of the variational matrix have a simple form which is easily evaluated, has a clear physical meaning and is directly interconnected with observed spectral effects. This allows preliminary estimation of spectral phenomena and correction of the molecular model to take account of experimental results. The use of contemporary methods of diagonalization of the variational matrix, which possesses a characteristic structure, facilitates a tenfold increase in the speed of the method in comparison with traditional methods.K. A. Timiryazev Agricultural Academy. Translated from Zhurnal Strukturnoi Khimii, Vol. 34, No. 1, pp. 141–148, January–February, 1993.     

Calculation of vibronic spectra of polyatomic molecules in the franck—condon and herzberg—teller approximations: Part I. Methods for calculating matrix elements

A number of methods, both accurate and approximate, have been developed to calculate the integrals arising in the theory of vibronic spectra of polyatomic molecules. These methods make it possible to calculate the vibrational structure of the electron spectra of polyatomic molecules in the most general approximations (one-electron, adiabatic) without imposing any particular restrictions (neglect of the Dushinsky effect, temperature distribution of molecules, etc.). A comparison is made of the suggested methods, the approximate methods are analyzed for limits of accuracy, and the optimal fields of application are pointed out.     

Synthesis of γ-mercuridinitrohydrocarbons

Summary The denitration of -mercurinitro compounds has been studied and the corresponding organomercury dinitro derivatives have been obtained.     

Application of artificial intelligence systems in molecular spectroscopy

The merits and demerits of data retrieval and artificial intelligence systems for identifying polyatomic molecules from their molecular spectra are considered. It is concluded that the creation of artificial intelligence systems provides the most promising developments for the future of analytical molecular spectroscopy. In these systems, experimental spectra are compared with computer-generated data in the course of solution of the analytical problem and not with data already stored in the data bank.     

Towards numerical vibrational spectroscopy

From the mathematical standpoint, it is possible to reduce a spectral study to the solution of the so-called inverse spectral problems. In practice, the inverse problem is solved through consistent comparison of the spectrum of the model with the experimental spectrum, the degree of closeness between theoretical and experimental spectra providing a quality criterion for the solution. The model may be characterized by different levels of complexity. This paper discusses the course of recent developments in theoretical spectroscopy, the present state-of-the-art, and forecasts future union of experimental and theoretical methods.