Frequencies Of Stretching Modes Research Articles

Infrared investigations of hydrogenated amorphous silicon. I. Inductive spectral shifts as predicted from monomer data

Abstract Using published i.r. frequencies, a linear correlation is demonstrated for the stretching mode frequencies of all -SiHn (n= 1-3) monomers, when plotted against the Hammett-Taft inductive substituent constant, σ. Extrapolation to a-Si: H (1) supports the presently accepted -SiHn assignments and (2) calls into question the existence of polysilane, (SiH2)n. Extension to other modes for CH3XSiH2 and X2SiH2 monomers, where X = halogen, showed internally consistent σ1 correlations for both series, although series-to-series consistency is lacking: this is demonstrated to arise from questionable peak assignments. Extrapolation of these modes to a-Si:H indicates that peaks are expected in the far-i.r. (<600cm−1), in agreement with recent theoretical and experimental results.

Relation between carbon–carbon bond length and compressibility from high pressure studies on liquid benzene

The frequency shift of the benzene ring stretching mode has been shown experimentally to be linear with pressure P over a range of about 10 kbar. Using Wilson’s formula for the free space molecule, arguing that the important force constant change with pressure is that associated with the carbon–carbon bond length l, and employing a semiempirical relation between force constant and l, value of dω/dl is determined, ω being the stretching mode frequency. Use of equation of state data on liquid benzene enables dω/dP to be calculated, in good agreement with experiment.

Infrared spectroscopic study of hydrogenated and deuterated silicon nitride films prepared from plasma-enhanced deposition

The infrared spectroscopic studies were carried out for plasma-enhanced chemical vapor deposition amorphous silicon nitride films prepared from gas systems which contain deuterosilane (SiD4) or deuteroammonia (ND3). The stretch-mode frequencies of N–H, N–D, Si–H, and Si–D bonds were observed at 3340, 2480, 2180, and 1585 cm−1, respectively. The absorption cross section of Si–D bond has been determined considering ratios of reduced masses and dipole moment derivatives for Si–H and Si–D bonds. As a result of the calculation of Si–H and Si–D bond concentrations using the respective absorption cross sections, the isotope effect on introduction ratio of H and D atoms bonded to Si atoms was not observed. Assuming that the isotope effect does not also affect the introduction ratio between N–H and N–D bond concentrations, the absorption cross section of N–D bonds is determined. It is also found that 80–90% of the total hydrogen atoms in the films are introduced from ammonia gas.

Infrared spectra of the matrix-isolated chlorides of iron, cobalt, and nickel

Iron, cobalt, and nickel metal cathodes were sputtered with various mixtures of 37Cl 2/ 35Cl 2/Ar to produce Ar matrices at 14 K that contained the mono-, di-, and trichlorides of the corresponding metal. The measured infrared absorption spectra of these matrices allowed the identification and characterization of FeCl 2, FeCl 3, CoCl, CoCl 2, CoCl 3, and NiCl 2. The derived vibrational constants of the electronic ground state of 59Co 35Cl are ω e = 457.8 ± 3.0 cm −1 and ω e χ e = 2.0 ± 1.5 cm −1. The antisymmetric stretching mode frequencies of six isotopomers of FeCl 2 and three isotopomers of CoCl 2 were identified and measured. The dichlorides of iron, cobalt, and nickel were all determined, in contrast with previous work, to be nonlinear with bond angles of 161, 157, and 161°, respectively. The estimated uncertainty is 5°. For both iron and cobalt trichlorides, the measured stretching mode frequencies were used to derive a ClMCl angle in excess of 120°, as would be expected for planar molecules with somewhat anharmonic vibrations. Observed adsorption peaks could be assigned to the ν 3( E) modes of planar ( D 3 h ) Fe and Co trichlorides and the corresponding modes of the isotopomers. These observations strongly suggest that recent data supporting a pyramidal geometry for FeCl 3 should be reexamined. The geometry of CoCl 3 has not previously been determined.

Precision raman measurements of some t d ions in aqueous solution

The Raman spectra of SO 4 2− , WO 4 2−, and MoO 4 2−, have been studied in aqueous solution with great, precision, and the effect of the alkali metal cations has been carefully recorded as a function of concentration. When Li + or Na + were present in solution, the anion vibrational frequency was observed to increase, with Li having the more pronounced effect. The cations K + , Rb + and Cs + caused the frequency to decrease, with Cs + causing the largest decrease, followed by Rb + and then K +. Precise values of the symmetric stretching mode frequencies at infinite dilution were obtained by extrapolation. The frequency shifts with respect to these values, were found Co depend on the square root of the concentration.

ChemInform Abstract: MATRIX ISOLATION INFRARED AND RAMAN SPECTRA OF BINARY AND MIXED GROUP II B FLUORIDES

AbstractDie IR‐ und Raman‐Spektren aller MFZ‐ und MEX‐Moleküle (M: Zn, Cd, Hg; X: Cl, Br) und das IR‐Spektrum von HgFI, in einer Kryptonmatrixbei 20 Kisoliert, werden angegeben.

Matrix isolation infrared and Raman spectra of binary and mixed group II B fluorides

Infrared and Raman spectra of all MF2 and MFX molecules (M=Zn, Cd, Hg; X=Cl, Br) and the infrared spectrum of the fluoroidide HgFI isolated in solid krypton at 20 °K are reported. The MFX species were formed in a vapor mixture of the appropriate MF2 and MX2 dihalides, vaporized, at different temperatures, from separate compartments of a double-oven crucible. The spectra are the first experimental evidence for the existence of the molecular fluorohalides. All three fundamentals of the MF2 molecules and the two stretching mode frequencies of the MFX molecules are assigned. Harmonic force constants are evaluated and isotope effects are used to discuss their geometry. Thermodynamic functions are tabulated for the binary difluorides.

Raman spectra of lanthanide sesquioxide single crystals with A‐type structure

AbstractPhonon data are given for La2O3, Pr2O3, and Nd2O3 single crystals. The polarized Raman spectra of Nd2O3 are presented and analysed according to Pauling's structure: D3d3 (P3ml), Z = 1. A factor group analysis leads to the symmetries 2A1g + 2 Eg for the q = O lattice vibrations which give a non zero contribution in the first order Raman scattering. The experimental data are in complete agreement with these previsions. The four Raman active vibrations are shown to be those of Ln2O(II)2 entities within cages of O(I) atoms, O(I) and O(II) lying in D3d and C3v crystal sites, respectively. There are two stretching (A1g + Eg) and two bending (A1g + Eg) modes, the assignments of which are made. A tentative comparison with the oxysulphides Ln2O2S, which have also a P3ml structure, is presented. A linear correlation is found between the Ln‐O(II) stretching mode frequency of the three studied sesquioxides and the c/a ratio of their hexagonal A‐type structure.

A critical evaluation of spectroscopic parameters from vibrational isotopic effects in matrix isolated MX 2 and MXY molecules (M = Zn, Cd, Hg; X, Y = Cl, Br, I)

The range of spectroscopic parameters (stretching and interaction force constants as well as bond angles) compatible with experimental errors in band positions and isotopic fine structure frequency differences are evaluated for the Group IIB binary and mixed dihalides from experimental data of stretching mode frequencies and isotopic splittings. The angle range includes the linear geometry for the zinc and cadmium dihalides but not for the HgX 2 and HgXY molecules. The approximations and assumptions inherent in the calculation are discussed.

ChemInform Abstract: FREQUENCIES OF GE‐H STRETCHING MODES AND THE EFFECT OF D PI‐P PI INTERACTION IN ORGANOGERMANIUM COMPOUNDS

Chemischer InformationsdienstVolume 5, Issue 48 Physical Organic Chemistry ChemInform Abstract: FREQUENCIES OF GE-H STRETCHING MODES AND THE EFFECT OF D PI-P PI INTERACTION IN ORGANOGERMANIUM COMPOUNDS A. N. EGOROCHKIN, A. N. EGOROCHKINSearch for more papers by this authorS. YA. KHORSHEV, S. YA. KHORSHEVSearch for more papers by this authorN. S. OSTASHEVA, N. S. OSTASHEVASearch for more papers by this authorJ. SATGE, J. SATGESearch for more papers by this authorP. RIVIERE, P. RIVIERESearch for more papers by this authorJ. BARRAU, J. BARRAUSearch for more papers by this authorM. MASSOL, M. MASSOLSearch for more papers by this author A. N. EGOROCHKIN, A. N. EGOROCHKINSearch for more papers by this authorS. YA. KHORSHEV, S. YA. KHORSHEVSearch for more papers by this authorN. S. OSTASHEVA, N. S. OSTASHEVASearch for more papers by this authorJ. SATGE, J. SATGESearch for more papers by this authorP. RIVIERE, P. RIVIERESearch for more papers by this authorJ. BARRAU, J. BARRAUSearch for more papers by this authorM. MASSOL, M. MASSOLSearch for more papers by this author First published: December 3, 1974 https://doi.org/10.1002/chin.197448084AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume5, Issue48December 3, 1974 RelatedInformation

The hydrated proton H+(H2O)n. II. A spectroscopic study and normal coordinate treatment of the oxonium ions H3O+ and D3O+

A spectroscopic study and a normal coordinate treatment (NCT) of the oxonium ions H3O+ and D3O+ in solid H3O+CH3C6H4SO3− and D3O+CH3C6H4SO3− were made. Neutron diffraction studies indicated a pyramidal, C3ν symmetry for the oxonium ions. Based on this symmetry, the observed frequencies for H3O+ and D3O+ were assigned and a NCT attempted using the general valence force field and the Urey-Bradley force field. Comparison of the fundamental vibrations in various oxonium compounds was made. It was demonstrated that a relationship between the OH stretching frequencies in H3O+ and D3O+ ions vs R (the O⋯O distance) exists, as well as a relationship between the stretching frequency shift (Δνs) and R. The failure of past investigators to recognize this trend may have contributed to the confusion regarding the assignments. This is the first confirmation of such a trend existing in oxonium compounds. It is suggested that the stretching mode frequencies in H3O+ and D3O+ are dependent on R. When Rx-y is greater than the X–H⋯Y van der Waals radius sum, the asymmetric stretching vibration (ν3,e) is at higher frequency than the symmetric stretching vibration (ν1,a1); where Rx-y is less, the stretching mode frequencies are inverted.

Structure, Vibrational Spectra, Dipole Moment, and Stability of Gaseous LiCN and LiNC

An ab initio Hartree–Fock calculation of the structure of gaseous LiCN and LiNC has been performed using a basis set of 84 uncontracted and 45 contracted Gaussian atomic functions. The calculated Li–C distance is 3.6317 a.u.; the calculated C–N distance is 2.1915 a.u. for linear LiCN. For linear LiNC the calculated Li–N distance is 3.3354 a.u.; the calculated N–C distance is 2.1857 a.u. No experimental gas-phase data have been reported, but the calculated C–N and N–C distances agree well with experimental C≡N bond lengths in other molecules. The calculated linear stretching mode frequencies are ν1 ≈ 2375, ν2 ≈ 670 cm−1 (6Li12C14N), and ν1 ≈ 2367, ν2 ≈ 785 cm−1 (6Li14N12C), agreeing with ν1 ≈ 2250 cm−1 for other molecules. For linear 6Li14N12C, a bending mode frequency of ≈ 250 cm−1 was calculated. The predicted dipole moment is very high (3–4 a.u.). A marginal energy difference of 0.0141 a.u. between LiCN and LiNC was found, LiNC being the more stable.

Vibrational Frequency Sum Rules for Distorted Complexes

The calculation of thermodynamic quantities that involve the change of frequencies due to distortion of octahedral complexes can be effectively simplified by calculating the mean frequency change within a vibrational type, rather than the change in each component individually. On the average each stretching mode frequency changes by the same amount, each bending mode frequency changes by the same amount, while the mixed mode frequencies change by amounts that depend on the percentages of stretching and bending motions in the mode.

The use of polarized infra-red radiation in the study of crystal structure

The relation between infra-red dichroism of a band produced by co-valent linkages in a crystal, and the direction of the changing dipole moment is treated quantitatively. Observations of dichroism have been made in a crystalline layer of adipic acid, and in a single crystal of diketopiperazine. The results agree with the crystal structures of the materials as derived from X-ray spectra, when the usual assumptions as to valency angles are made in calculating NH, CH and OH bond directions. The stretching mode frequencies of NH in diketopiperazine consist of at least six peaks, all showing exactly the same dichroism. The breadth of the OH band in adipic acid can perhaps be explained as being due to rotation of the OH group around the single bond CO link.