Jiro Hiraishi

Force constants of CF4, SiF4, BF3, CH4, SiH4, NH3, and PH3

Abstract The general force constants are calculated from the observed frequencies, the Coriolis coupling constants and the available isotope shifts of frequencies for CF 4 and SiF 4 . The off-diagonal force constants obtained are explained by the Lennard-Jones type nonbonded fluorine-fluorine interaction. The vibration frequencies, their isotope shifts and the Coriolis constants of BF 3 are also explained by the same interaction. Force constants of CCl 4 , CBr 4 , CI 4 , SiCl 4 , SiBr 4 , SiI 4 , BCl 3 , BBr 3 , and BI 3 are obtained by similar methods. For CH 4 , SiH 4 , NH 3 , and PH 3 a set of the elements of F -matrices has been obtained which gives the vibrational frequencies of these molecules, those of CH 3 D, CH 2 D 2 , CHD 3 , CD 4 , SiD 4 , ND 3 , and PD 3 and the Coriolis coupling constants in agreement with the observed ones. The magnitudes of the obtained off-diagonal elements are discussed. They are in agreement with those calculated from Buckinghams nonempirical formula for the hydrogen-hydrogen nonbonded interaction.

Infrared spectra of some hexahalogeno complexes

Abstract Infrared spectra of hexachloro complexes have been measured from 14 to 35 μ. A strong band observed in the range 350 ∼ 300 cm −1 was assigned to the triply degenerate stretching vibration, ν 3 . A normal co-ordinate treatment has been made for these complex ions on the basis of the molecular force field adequate for some hexafluorides. The nature of metal-halogen co-ordination bonds has been discussed on considering the bond stretching force constants obtained. The result is in agreement with that of the pure quadrupole resonance study of halogens.

Correction of finite slit width effects on Raman line widths

Abstract An equation is derived for the correction of the finite slit width effect on line widths of Lorentzian Raman lines. It holds for up to S/δa = 0.7, more applicable than those proposed previously. A method is also proposed for obtaining the true isotropic line width from observed parallel and perpendicular polarized spectra.

Lattice vibrations and the force field of K2PtCl4, K2PdCl4 and K2PtCl4

Abstract The far infra-red spectra of K 2 PtCl 4 , K 2 PdCl 4 and K 2 PtCl 6 have been measured in the frequency region from 500 to 600 cm −1 and a normal co-ordinate treatment has been made for these compounds on considering the lattice vibrations. It has been shown that the modified Urey-Bradley force field is adequate for K 2 PtCl 4 . The potential functions between K + ion and Cl atom has been discussed.

Far infra-red spectra and force constants of ammine complexes of Pt(IV), Pt(II) and Pd(II)

Abstract Far infra-red spectra of [Pt(NH 3 ) 6 ] 4+ , [Pt(NH 3 ) 4 ] 2+ , trans - and cis -[PtCl 2 (NH 3 ) 2 ], [PtCl 3 (NH 3 )] − , cis -[PtBr 2 (NH 3 ) 2 ], [Pd(NH 3 ) 4 ] 2+ and trans -[PdCl 2 (NH 3 ) 2 ] have been measured in the frequency region down to 60 cm −1 . The assignments of the observed bands have been made on the basis of the frequency calculation. The metal—nitrogen in-plane bending vibrations appear in the frequency region from 300 to 200 cm −1 and the metal—nitrogen out-of-plane bending vibrations from 250 to 180 cm −1 . For [Pt(NH 3 ) 4 ][PtCl 4 ], [Pt(NH 3 ) 4 ][PtBr 4 ], [Pd(NH 3 ) 4 ][PdCl 4 ] and [Pd(NH 3 ) 4 ][PdBr 4 ], the far infra-red spectra have also been measured and the assignments have been made consistently. The bands appearing around 200 cm −1 , which shift to higher frequency region and become strong at liquid nitrogen temperature, are assigned to the A 2 u lattice vibration having high frequency by the strong metal—metal interaction. The nature of the co-ordination bonds has been discussed on the basis of the force constants obtained.

Comparative study of Raman and i.r. band widths of acetonitrile

Abstract Raman and i.r. band widths of all the vibrational bands of acetonitrile, CH 3 CN and CD 3 CN, have been measured in the pure liquid and in solutions of isotopic compounds. Widths arising from the vibrational relaxation, reorientational relaxation and resonance energy transfer have been separated on the basis of the current theories on vibrational band widths. The vibrational relaxation widths estimated for i.r. a 1 bands agree well with the observed isotropic Raman widths. Acceptable values of the rotational diffusion constants have been obtained from the band width data.

Experimental Determination of True Raman Linewidths from Measurements of Linewidths Observed at Different Slit Openings

A method is proposed to determine a true Raman linewidth from linewidths observed at different slit openings, without knowing accurate spectral slit widths. It is applied to various Raman lines of liquid molecules to assess the utility of the method.

Identification of Chemical Structures from Infrared Spectra by Using Neural Networks

Structure identification of chemical substances from infrared spectra can be done with various approaches: a theoretical method using quantum chemistry calculations, an inductive method using standard spectral databases of known chemical substances, and an empirical method using rules between spectra and structures. For various reasons, it is difficult to definitively identify structures with these methods. The relationship between structures and infrared spectra is complicated and nonlinear, and for problems with such nonlinear relationships, neural networks are the most powerful tools. In this study, we have evaluated the performance of a neural network system that mimics the methods used by specialists to identify chemical structures from infrared spectra. Neural networks for identifying over 100 functional groups have been trained by using over 10 000 infrared spectral data compiled in the integrated spectral database system (SDBS) constructed in our laboratory. Network structures and training methods have been optimized for a wide range of conditions. It has been demonstrated that with neural networks, various types of functional groups can be identified, but only with an average accuracy of about 80%. The reason that 100% identification accuracy has not been achieved is discussed.

Truncation effects on second moments of vibrational bands

Abstract The truncation effect on the second moment of a vibrational line shape is examined in detail on the basis of the assumed time correlation function. The magnitude of the effect is evaluated as a function of the line shape parameter and of the truncation limit. The results indicate that the integration has to be carried out more than 50 times as wide as the line width for obtaining an accurate second moment from the direct integration. An approximate method to correct the truncation effect is proposed.

Infrared Spectra and Metal-Ligand Force Constants in Coordination Compounds

Infrared spectra of metal complexes have already been intensively studied and the effects of a metal ion on the vibration frequencies in the ligand have been investigated (1). However, not so many investigations have been reported for the metal-ligand stretching and deformation vibrations. Recently we have measured the low frequency infrared spectra of ammine, halogeno, nitro, cyano, aquo and isothiocyanato complex ions. The assignments of the bands observed have been made on the basis of a normal coordinate analysis and the force constants associated with the metal-ligand bonds have been obtained. The results may be useful for the understanding of the nature of the metalligand bonds and give further information on the already recognized tendencies of electrons (2). The present paper is a summary of the results of our study.