Infrared intensity analysis of CH2Cl2 and CD2Cl2 in vapour and liquid states

In the infrared spectra of molecules with more than one C-H bond the symmetric and antisymmetric stretching bonds often overlap, causing uncertainty in the intensity analysis. For CH₂Cl₂ and CD₂Cl₂ in the vapour state, the two bands overlap to such an extent that Straley who takes it as one band attributes it to antisymmetric stretching while Saekiet al assign it to the symmetric stretching. Following the method of analysis initiated in this laboratory, we have solved this problem by ultimately obtaining intensities separately forA ₁ andB ₂ species. The band is mostly due to the symmetric stretching, 0.06 out of the total of 0.31 contributing toB ₂. Thus, this gives a method of separating the intensities of bands which are highly overlapping. Presented at the Symposium on Crystallography and Crystal Physics, Osmania University, Hyderabad held on 5–7, December 1977.     

Raman and infrared intensity analysis of CHCl3 and CDCl3

Raman and infrared intensity analysis of CHCl₃ is attempted to determine the bond polarisability derivatives and bond dipole moments and their derivatives respectively, on lines expained in our earlier papers.     

Calculation of force constants and mean amplitudes of vibration of octahedral XY6 molecules using frequencies and zeta constants

Expressions involving vibrational frequencies, Coriolis coupling constants and masses of the atoms of the molecule that are invariant under symmetrical isotopic substitutions are derived for octahedral XY₆ molecules following the method given by Jagannathan and others. These invariants are used to calculate the force constants, compliance constants and mean amplitudes of vibration of 13 molecules of XY₆-type.     

Infrared intensity analysis of some MXY2 type molecules

Infrared intensity analysis of MXY₂ type molecules has been attempted. The dipole momentμ of C=O is obtained to be different for different moleculesviz. for CH₂O, 1.9052; for COCl₂, 1.1517; for COF₂, 0.6340; and for COBr₂, 0.7687. Similarly in the case of CSF₂ and CSCl₂ μ _C=S it was found to be 0.2473 and 0.2983 respectively. This shows that the effect of the electro-negative halogen atoms is very important. Presented at the ‘National Symposium on Molecular Spectroscopy’, Annamalai University, Annamalainagar on 28 February 1976.     

采用中子衍射实验解析PbS的原子间力常数

使用日本原子能研究开发机构里设置的高分解能粉末中子衍射装置, 在 15 K 和 294 K 温度下对 PbS 进行了中子衍射实验。在 15 K 和 294 K 温度里观察到了明显的振动形状的热漫散射。 所观察到的漫散射强度可由原子间热振动相关效应的影响来解释。在 294 K 下从原子间相关效应和德拜—劳厄因子的温度参数中获得了 PbS 相邻原子间的力常数。     

Raman and Infrared Spectra of Cd(15NH3)2Cl2 and Local Symmetry Force Field

The infrared and Raman spectra of Cd(¹⁵NH₃)₂Cl₂ are reported and a comparison is made between the normal and ²H isotope substituted compounds. A further refinement of the Local Symmetry Force Constants was carried out.     

采用中子衍射实验解析PbS的原子间力常数

使用日本原子能研究开发机构里设置的高分解能粉末中子衍射装置,在15 K和294 K温度下对Pb S进行了中子衍射实验.在15 K和294 K温度里观察到了明显的振动形状的热漫散射.所观察到的漫散射强度可由原子间热振动相关效应的影响来解释.在294 K下从原子间相关效应和德拜-劳厄因子的温度参数中获得了Pb S相邻原子间的力常数.     

Presentation of Molecular Force Fields in Terms of Dimensionless Coordinates

It is suggested that force fields calculated for polyatomic molecules may be presented in dimensionless coordinates, ξ (=R/R_e, where R is internal coordinate and Re is the equilibrium value of corresponding bond distance or angle). Stretching force constants when presented in dimensionless coordinates show interesting trends. It is found that whereas the force constants in terms of internal coordinates, F_ii vary widely for bonds with different atoms in the series Z-H (Z:C, Si, Ge), Y-H (Y:N, P, As, Sb, O, S), X-H (X:F, Cl, Br, I), X-C etc, the corresponding force constants in dimensionless coordinates, Φ_ii are same within the limits of experimental errors. It is felt that such force constants may have better prospects of transferability between related molecules and may be helpful in making the normal coordinate analysis easier to some extent.     

Vibrational Spectra of Cd(NH3)2Cl2 with 2H Isotopic Substitution

The infrared and Raman spectra of the cadmium diammindichloride complexes with ²H isotopic substitution, have been measured. A normal coordinate analysis for the isotopic compounds has been carried out based on a Local Symmetry Force Field (LSFF). The results sup port the experimental assignments.     

On the calculation of force constants using isotopic frequencies by parametric method: Application to systems of (3×3) order

A method is proposed for the determination of angle parameters for ONF, ONCl and ONBr, utilising the isotopic frequencies of two isotopically substituted molecules. The force constants, Coriolis coupling constants, inertia defect, mean amplitudes of vibration and rotational distortion constants were also calculated and compared with literature values.     

Vibrational Spectra of Cd(NH3)2Br2 with 2H Isotopic Substitution and Local Symmetry Force Field

The infrared and Raman spectra of the cadmiumdiammindibromide with ²H - isotopic substitution, have been measured. In order to examine the transferabilities of the skeletal and -NH₃, ligand force constants, a normal coordinate analysis was carried out based on a Local Symmetry Force Field (LSFF). The results support the experimental assignments.     

On the determination of the intramolecular potential energy surface of polyatomic molecules: Hydrogen sulfide and formaldehyde as an illustration

We present here an approach for determining the Hamiltonian of polyatomic molecules that allows one to successfully solve the problem of potential energy surface (PES) determination via construction and diagonalization of a Hamiltonian matrix of large dimension. In the suggested approach, the Hamiltonian is very simple and can be used both for any “normal” polyatomic molecule and for any isotopic species of a molecule. Molecules with two to four equivalent X-Y bonds are considered, and for illustration of the efficiency of the suggested approach, numerical calculations are made for the three-atomic (hydrogen sulfide) and four-atomic (formaldehyde) molecules.     

Molecular constants of XeO3F2

The force constants of XeO₃F₂ have been evaluated using the general valence force field. The mean square amplitudes of vibration, the generalised mean square amplitudes and shrinkage constants, Coriolis coupling coefficients and centrifugal distortion constants have also been calculated for the first time using the vibrational frequencies and the structural parameters. The thermodynamic properties have been computed for the ideal gaseous state at 1 atmospheric pressure for 11 temperatures from 100° to 1000°K using a rigid rotor harmonic oscillator approximation.     

Molecular constants of SiH3C ≡ CH and SiD3C ≡ CH

A normal co-ordinate analysis of silylacetylene and silylacetylene-d ₃ has been carried out following Wilson'sF-G matrix method. The potential energy constants obtained therefrom have been used to evaluate rotational distortion constants and mean square amplitudes of vibration for these molecules. Thermodynamic functions, such as heat content, free energy, entropy heat capacity for the ideal gaseous state at one atmosphere pressure and with the usual rigid rotor harmonic oscillator approximation, have also been calculated for 12 temperatures from 100°K to 1000°K.     

Anharmonic force constants of GaSb from the measured third order elastic constants at 300°K

The third-order elastic constants of single crystal GaSb are determined using ultrasonic pulse interferometer at 10 MHz. The constants at 300°K, in units of 10¹¹ N.m.⁻², are C_l11 = ™ 4 ·75 ± 0·06 C₁₄₄ = + 0·50 ± 0·25 C₁₁₃ = ™ 3 ·08 ± 0·02 C₁₆₆ = ™ 2·16 ± 0·13 C₁₂₃ = ™ 0 ·44 ± 0·29 C₄₅₆ = ™ 0·25 ± 0·15 These constants are used to evaluate the three anharmonic first and second neighbour force constants based on modified Keating’s model. The constants are (in units of 10¹¹ N.m⁻²)γ=− 2·406;δ=0·407;ε=−0·222.     

Studies on dissociation energies of diatomic molecules using vibrational spectroscopic constants

New analytical expression and numerical approach are suggested to calculate dissociation energies De of diatomic molecular states using an extreme value method (EVM). Studies on some electronic states of OH, BH, N2, Br2, ClF and CO molecules show that the accuracy of the EVM dissociation energies depends on the number of correct vibrational constants used in the calculations. The convergence qualities of De are suggested to be an alternative physical criterion to measure the qualities of the various sets of vibrational constants from different literature for the same diatomic state.     

Anisotropies in carbon-13 chemical shift tensor,H-C-H bond angles and the signs of the coupling constants in 13CH3I, 13CH3Br, 13CH3Cl

A pulsed fast Fourier transform N.M.R. spectrometer is used to investigate the temperature dependence of the ¹³C chemical shifts in the nematic liquid crystal solutions of the following halides: ¹³CH₃I, ¹³CH₃Br, ¹³CH₃Cl. The H-C-H bond angles are accurately measured in this investigation from proton magnetic resonance studies. The signs of the coupling constants D _13CH , D _HH, J _13CH and the ordering parameter have been assigned to be all positive. The ¹³C magnetic shielding anisotropy is found to become more positive with the increasing electronegativity of the halogen substituents. The values of the anisotropies are: Δσ = σ _∥ - σ _⊥ = - 101 ± 15 p.p.m. (¹³CH₃I), - 10 ± 5 p.p.m. (¹³CH₃Br), 22 ± 5 p.p.m. (¹³CH₃Cl). Results for Δσ obtained from the slope of σ_n versus S ₃₃ agree with those obtained from the nematic-isotropic phase subtraction method.