Cartesian Dynamics of Simple Molecules. IX. Pyramidal Quadratomics (C3v Symmetry)

The vibrations of pyramidal AB₃ type molecules with C_3v symmetry are analyzed in terms of Cartesian co-ordinates, and analytical expressions for the four normal mode frequencies are derived as functions of two stretching and two bending force constants. Optimized values of these force constants are obtained for a number of tri-hydride and tri-halide molecules by substitution of available spectroscopic and geometric data. The physical validity of the model is confirmed by comparing the calculated and observed frequencies of several isotopic species.     

Absolute Intensities of Spectral Lines in the Q-Branch of the CH3D at Low Temperature

Abstract

We report the absolute intensities of 38 lines of the Q branch of the v₂ band of CH₃D near 2200 cm^?1, obtained at 98.3 K, using a Fourier Transform spectrometer with a resolution of 0.006 cm^?1     

Cartesian Dynamics of Simple Molecules III Non-Linear Triatomics (C2v Symmetry)

A simple spring model for the molecular vibrations of non-linear triatomic molecules with C_2v symmetry is described in terms of Cartesian co-ordinates. Analytical expressions for the stretching and bending mode frequencies are obtained and compared with previous derivations. Optimized values of force constants are calculated for models involving two or three adjustable parameters. The validity of the model is demonstrated by the satisfactory agreement between calculated and observed frequencies of isotopic species. The model provides a simple explanation of the near degeneracy of the symmetric and asymmetric stretching frequencies of H₂S and H₂Se.     

Vibrational Mean Amplitudes of XY3 Pyramidal Molecules

The vibrational mean amplitudes for bonded as well as for nonbonded distances have been evaluated for AsP₃, SbP₃, and PAs₃ at temperatures : T = 0^oK, T = 298.15^oK and T=500 ^oK using recent vibrational data. The results have been briefly discussed.     

Determination of Orientation Averages for Partially Aligned low Symmetry Molecules

A graphical procedure is presented which allows a determination of the average alignment of the molecular axes in partially oriented, low-symmetry planar molecules from the results of linear dichroism and fluorescence polarization spectroscopy. When applied to benz[a]anthracene, the method makes it possible to extract information on the previously unknown origin of the second excited electronic state.     

Spectroscopy of XY(5)Z (C(4v)) Molecules: A Tensorial Formalism Adapted to the O(3) superset O(h) superset C(4v) Chain

A tensorial formalism adapted to the case of XY(5)Z symmetric tops has been developed as an extension of the usual one for the octahedral molecules. We use the O(3) superset O(h) superset C(4&v) group chain. All the coupling coefficients and formulas for the computation of matrix elements are given for this chain. Such relations are also deduced in the C(4v) group itself. Copyright 2000 Academic Press.     

Experimental Ro-Vibrational Line Intensities for the v1 + v2 and v2 + v3 Bands of the D234S Molecule

Russian Physics Journal - The study of the absolute line intensities in the high-resolution spectrum of the D234S molecule in the range of 2300–2900 cm–1 has been carried out for the...     

Absolute Intensities of the Infrared Bands of Gaseous Acrylonitrile

Laboratory spectral data (peak positions and integrated band intensities) of the infrared bands of acrylonitrile (CH2CHCN) gas in the region 4000-220 cm-1 are presented. Even though CH2CHCN has not yet been identified in Titan's atmosphere, it is among the possible photochemical and cosmic irradiation products of CH4 + N2 chemistry in the atmosphere of Titan. Laboratory simulations of Titan's atmospheric chemistry also give CH2CHCN as a product species. The results of our evaluation of the infrared intensity data provide an upper limit of the stratospheric abundance of CH2CHCN. Copyright 1999 Academic Press.     

Intensities and line shapes in the v2-fundamentals of 14NH3 and 15NH3

Spectral transmission measurements in the v^s₂- and v^a₂-fundamentals of ¹⁴NH₃ and ¹⁵NH₃ have yielded information that is valuable in the interpretation of spectroscopic scans of Jupiter covering the thermal infrared between 9 and 12 μm. Our experimental data demonstrate that the absorption spectra of the two species of NH₃ differ from each other only in line positions but not in the strengths, widths or shapes of lines with the same quantum number designations.     

Spectroscopy of XY(5)Z (C(4v)) Molecules: Development of the Hamiltonian and the Transition Moment Operators Using a Tensorial Formalism

We present a development of the Hamiltonian, dipole moment, and polarizability operators of XY(5)Z (C(4v)) molecules using a tensorial formalism derived from the one developed previously in Dijon for XY(6) molecules. These operators are involved in the calculation of the energies and intensities of rovibrational transitions and are essential for spectrum simulations. Expressions for the matrix elements are derived for all these operators. Copyright 2000 Academic Press.     

Calculation of Absorption Intensities of Cr3+ Ion Pair Lines in Ruby

The calculation of relative intensities of the optical absorption lines of the fourth order pair of Cr³⁺ ions in ruby has been performed assuming the electro-dipole character of the transitions.     

On the Relative Intensity-Concentration Relationship of Carbonyl Bands in the Solution Infrared Spectra of Metal Carbonyl Compounds of C4v Symmetry

The theory on the relative intensities of CO stretching bands of metal carbonyl compounds of C^4v symmetry has been advanced by orgel, inter alios. ² For complexes of formula M(CO)₅Xⁿ [a = -1, 0), three infrared active bands are expected, 2A₁ + E. The two A₁ bands consist of modes which are predominantly vibration of the CO trans to X (A₁ ⁽¹⁾) and the symmetrical stretch of the four equatorial CO's (A^{1 (2)}). The A₁ ⁽²⁾ band is nearly forbidden, and owes its intensity to the contribution of the axial CO stretch to the normal mode. The end result of this coupling between axial and radial CO stretching symmetry modes would appear to be an aid in assigning the bands in the carbonyl stretching region to the appropriate symmetry modes; the relative intensities are weak (A₁ ⁽²⁾), strong (E), and medium (A₁ ⁽¹⁾) Although this weak-strong-medium pattern is invariably observed in the spectra of     

由拉曼谱线强度变化研究C_(60)分子的内模振动

由拉曼谱线强度变化研究Ｃ６０分子的内模振动王建模高长连刘正东１）陶向阳辛建之罗宏雷２）肖新民（江西师范大学物理系南昌３３００２７）（１）浙江大学物理系杭州３１００２７）（２）杭州三维高科技产业公司杭州３１００１２）ＳｔｕｄｙｔｈｅＩｎｎｅｒ┐Ｍ...     

Absolute Line Intensities for the nu6 Band of H2O2

The purpose of this work was to obtain reliable absolute intensities for the nu6 band of H2O2. It was undertaken because strong discrepancies exist between the different nu6 band intensities which are presently available in the literature (A. Perrin, A. Valentin, J.-M. Flaud, C. Camy-Peyret, L. Schriver, A. Schriver, and P. Arcas, J. Mol. Spectrosc. 1995. 171, 358), (R. May, J. Quant. Radiat. Transfer 1991. 45, 267), and (R. L. Sams, personal communication). The method which was chosen in the present work was to measure simultaneously the far-infrared absorptions and the nu6 absorptions of H2O2. Consequently, Fourier transform spectra of H2O2 were recorded at Giessen in a spectral range (370-1270 cm-1) which covers both the R branch of the torsion-rotation band and the P branch of the nu6 band which appear at low and high wavenumbers, respectively. From the low wavenumber data, the partial pressure of H2O2 present in the cell during the recording of the spectra was determined by calibrating the observed absorptions in the torsion-rotation band with intensities computed using the permanent H2O2 dipole moment measured by Stark effect (A. Perrin, J.-M. Flaud, C. Camy-Peyret, R. Schermaul, M. Winnewisser, J.-Y. Mandin, V. Dana, M. Badaoui, and J. Koput, J. Mol. Spectrosc. 1996. 176, 287-296) and [E. A. Cohen and H. M. Pickett, J. Mol. Spectrosc. 1981. 87, 582-583). In the high frequency range, this value of the partial pressure of H2O2 was used to measure absolute line intensities in the nu6 band. Finally, the line intensities in the nu6 band were fitted using the theoretical methods described in detail in our previous works. Using these new results on line intensities together with the line position parameters that we obtained previously, a new synthetic spectra of the nu6 band was generated, leading to a total band intensity of 0.185 x 10(-16) cm-1/(molecule.cm-2) at 296 K. It has to be pointed out that the new line intensities agree to within the experimental uncertainties with the individual line intensity measurements performed previously by May and by Sams. Copyright 1999 Academic Press.     

Absolute Intensities of the nu(1) and nu(3) Bands of (16)O(3)

New experimental data on the nu(1) and nu(3) bands of (16)O(3) improving the value of absolute line intensities have been obtained. The intensities of 295 lines have been measured with an average accuracy between 2.5% and 3% and the rotational expansion of the transition moment operators for the nu(1) and nu(3) bands has been deduced. Finally, a complete listing of line intensities has been computed with an intensity cutoff of 1x10(-25) cm(-1)/molecule cm(-2). Copyright 2001 Academic Press.     

H12C14N分子v2垂直带的高温谱线强度及随温度的变化规律

采用乘积近似法计算了氰化氢分子H12C14N的总配分函数,其中转动配分函数考虑了离心扭曲修正,振动配分函数采用谐振子近似.利用计算所得配分函数和文献提供的实验振动跃迁矩平方及HermanWallis因子系数,计算了氰化氢分子H12C14Nv2垂直带,即0110-0000跃迁在常温和高温下的线强度,并与HITRAN数据库的数据进行了比较.结果显示,在296 K及温度高达3 000 K时,计算所得谱线强度与HI-TRAN数据库提供的结果均符合较好.表明对氰化氢分子H12C14N高温下的分子配分函数和线强度的计算是可靠的.进一步计算了0110-0000跃迁带在更高温度4 000和5 000 K的线强度及模拟光谱,并总结了该跃迁带中的谱线强度随温度的变化规律:对于转动量子数J≥32的跃迁谱线(包括P支、Q支和R支),当温度从296.K逐渐增加时,其线强度迅速增加,到1 000 K附近达到最大值,然后迅速减弱.对于转动量子数J<32的跃迁谱线(同样包括P支、Q支和R支),线强度在296 K时最大,然后随温度的升高迅速减弱.     

Infrared transitions of C2D6 from v 4 to the interacting system v 4+ v 6, v 4+ v8, v 3+ 2v 4: rotational analysis,and torsional splitting in the v 3+ 2v 4 and v 3+ v 4 states

The hot infrared transitions of C₂D₆ from the υ₄(A_1u ) to the υ₄ + υ₆(A_2g ) and υ₄ + υ₈(E _g ) vibrational states, observed from 960 to 1180 cm^?1, have been rotationally analysed on a high-resolution Fourier transform spectrum (full width at half-maximum about 0·0030 cm^?1). The vibration-rotation interactions affecting the upper vibrational states are very similar to those of the corresponding cold system. A strong x,y Coriolis interaction between υ₄ + υ₆ and υ₄ + υ₈, with K-level crossing, generates large displacements of the rotational components of both vibrational states, tuning them to additional local resonances in several spectral regions. Thus l resonances with Δl = ±2, Δk = ±1 occur within υ₄ + υ₈. A x,y Coriolis-type resonance between υ₄ + υ₈(?l,K ? 1) and υ₃ + 2υ₄(K) occurs at K = 11,12,13, and a further coupling of υ₄ + υ₈(+l,K + 1) and υ₃ + 2υ₄(K + 3) is most effective at K = 11 and 12. These resonances induce torsional splittings on the perturbed levels of υ₄ + υ₈ and allow us to determine the torsional splittings in the υ₃ + 2υ₄ state. The vibration-rotation constants of υ₄ + υ₆, υ₄ + υ₈ and υ₃ + 2υ₄, several interaction parameters and the torsional splitting of υ₃ + 2υ₄ have been determined by least-squares fit of 1391 observed transition wavenumbers, with an overall standard deviation σ = 0·75 × 10^?3 cm^?1. The vibrational wavenumbers found for the four torsional components of (υ₃ + 2υ₄)? υ₄ are υ(E_3d) = 1040·961 82(809)cm^?1, υ(A_3d) = 1041·218 27(865)cm^?1, υ(E_3s) = 1041·225 23(662)cm^?1 and υ(A_1s) = 1041·407 77(633)cm^?1. These are anomalous for both the order of the torsional components and the magnitudes of their separations. We believe that this is mainly due to the interactions of υ₃ + 2υ₄ with the torsional manifolds with υ₃ = 0 and υ₃ = 2, through the vibration-torsion Hamiltonian term (?V ₆/?q ₃)q ₃cos (6γ)]/2. The further observation of a few doublets of υ₈ and υ₃ + υ₄ at resonance provides information on the torsional splitting of the latter state.