Calculation of band intensities in vibrational spectra and conformation of chloromethylformate and chloromethylacetate

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 49, No. 1, pp. 70–74, July, 1988.     

Theoretical study of IR band intensities and electronic transition moments for the β and δ systems of NO

The variation of the electronic transition moment with internuclear separation has been calculated for the beta and delta systems of NO. Theoretical band intensities for the fundamental and first two overtones have also been calculated for the ground state. The results are based on the self-consistent-field plus configuration-interaction technique, and they are compared with the existing experimental data. Theoretical potential-energy curves and the spectroscopic constants T_e, r_e, ω_e, and ω_eχ_e for the X²π, B²π, and C²π electronic states of NO are also reported.     

Raman band intensities of tellurite glasses

Raman spectra of TeO2-based glasses doped with WO3, ZnO, GeO2, TiO2, MoO3, and Sb2O3 are measured. The intensity of bands in the Raman spectra of MoO3-TeO2 and MoO3-WO3-TeO2 glasses is shown to be 80-95 times higher than that for silica glass. It is shown that these glasses can be considered as one of the most promising materials for Raman fiber amplifiers.     

Calculation of dipole moment functions with density functional theory: application to vibrational band intensities

We have calculated fundamental and overtone XH stretching vibrational band intensities for H₂O, benzene, cyclohexane, 1,3-butadiene, and HCN. The band intensities were calculated with a simple harmonically coupled anharmonic oscillator local mode model and a series expanded dipole moment function. The dipole moment functions were obtained from local, non-local and hybrid density functional theory calculations with basis sets ranging from 6–31G(d) to 6–311++G(3df,3pd). The calculated band intensities have been compared with intensities calculated with conventional ab initio methods and with experimental results. Compared with conventional correlated ab initio methods, a carefully chosen density functional method and basis set seems to give better fundamental and overtone intensities with far less resources used. We have found that the density functional methods appear to be less sensitive to the choice of basis set, with little difference between the results obtained with a non-local or hybrid density functional method.     

Carbamate-group conformation and IR band intensities

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 53, No. 2, pp. 270–275, August, 1990.     

Infrared band intensities for isotopic water molecules

Integrated intensities for the three fundamental i.r. bands of HOD, DOD, HOT and TOT are estimated theoretically using Crawford's method. Experimental values have only been reported for HOD; agreement is found to ±8%.     

Measurements of line intensities in the two-micron band of ammonia

Intensities of about four hundred lines of ammonia in the 2μ region have been measured using Doppler-broadened lines. Comparison with rigid-rotor calculations gives fair agreement between theory and experiment. The total integrated intensity of the ν₃ + ν₄ (perpendicular) band has been estimated to be 17.19 cm^-2 atm^-1 at 296 K.     

Absolute integrated intensity and individual line parameters for the 6·2μ band of NO2

The absolute integrated intensity of the 6·2μ band of NO₂ at 40°C was determined from quantitative spectra at ~ 10 cm^?1 resolution by the spectral band model technique. A value of 1430±300 cm^?2 atm^?1 was obtained. Individual line parameters, positions, intensities and ground state energies were derived, and line-by-line calculations were compared with the band model results and with the quantitative spectra obtained at ~ 0·5 cm^?1 resolution.     

Bond charge parameters from integrated infrared intensities

A procedure is outlined to analyze the infrared absorption intensities of fundamental vibration bands in terms of “bond charge parameters”. The method is illustrated for some small C_2v- and C_3v-type molecules: SO₂, NF₃, and PF₃. The values obtained for the “bond charge reorganizations” and “effective bond charges” for SO, NF, and PF bonds are discussed. The method offers the possibility of calculating rotational contributions without the use of a reference molecule.     

Quantitative measurement of integrated band intensities of benzene vapor in the mid-infrared at 278, 298, and 323 K

Pressure broadened (1 atm. N₂) laboratory spectra of benzene vapor (in natural abundance) were recorded at 278, 298, and 323 K, covering 600-6500 cm⁻¹. The spectra were recorded at a resolution of 0.112 cm⁻¹ using a commercial Fourier transform spectrometer. The pressure of each benzene vapor sample was measured using high-precision capacitance manometers, and a minimum of nine sample pressures were recorded for each temperature. The samples were introduced into a temperature-stabilized static cell (19.94(1) cm pathlength) that was hard-mounted into the spectrometer. From these data a fit composite spectrum was calculated for each temperature. The number density for the three composite spectra was normalized to 296 K. The spectra give the absorption coefficient (cm² molecule⁻¹, naperian units) as a function of wavenumber. From these spectra integrated band intensities (cm molecule⁻¹ and atm⁻¹ cm⁻²) for intervals corresponding to the stronger benzene bands were calculated and were compared with previously reported values. We discuss and quantify error sources and estimate our systematic (NIST Type-B) errors to be 3% for the stronger bands. The measured absorption coefficients and integrated band intensities are useful for remote sensing applications such as measurements of planetary atmospheres and assessment of the environmental impact of terrestrial oil fire emissions.     

Calculation of Raman intensities by a CNDO method

A variational method for calculation of Raman intensities within the polarizability theory is formulated. The CNDO approximation is inworked, and the basis set is extended to include polarization functions. The numerical results obtained for the ethylene molecule compare well with experiments.     

Calculation of RHEED intensities by a THEED algorithm

RHEED intensities from Si(111)1 × 1 are calculated using the Cowley-Moodie algorithm developed for transmission electron diffraction. The intensities are close to those calculated by the standard algorithms employed in RHEED. The Cowley-Moodie algorithm may be the best means of calculating RHEED patterns from surfaces with long periods such as Si(111)7 × 7 or from disordered surfaces.     

Analysis of band intensities in vibrational spectra of esters and deuteroesters

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 4, pp. 570–574, April, 1991.     

The integrated intensity of the nitric oxide fundamental band

The integrated intensity of the NO fundamental at 1875 cm^-1 has been measured by the Wilson-Wells method. The intensity of this band was found to be 135±5 atm^-1cm^-2 (S.T.P.), in good agreement with the intensity found by other experimental methods.