V3 Band Research Articles

Far infrared stimulated emissions from CO2 laser excited dichloromethane

Six new far-infrared laser frequencies have been obtained in CO2-laser excited dichloromethane. Competing transitions have enabled assignments to be made to the v7 band.

Quantum assignments and intensity measures for methane between 1100 and 1800 per CM - A comparison between theory and experiment

The paper analyzes line positions and absolute line strengths of Blatherwick et al. (1979), based on moderately high resolution spectra of methane between 1100 and 1800 per cm, obtained using the Fourier transform spectrometer and the multiple-pass cold cell at the NASA Ames Research Center. Hamiltonian models are used to calculate theoretical relative line strengths, which, in combination with measured line strengths, yield integrated band strengths for the fundamentals v2 and v4. Ratios of calculated intensities to experimental intensities are analyzed, and the systematic deviations in the P- and R-branches of the v2 band are found to be represented by a Herman-Wallis type factor for Coriolis interactions. An analysis of ratios of calculated to experimental intensities of the v4 band yields a small correction to the Herman-Wallis factor.

Anharmonic and Coordination Effects on Water in Magnesium Perchlorate Hexahydrate

The infrared (IR) spectra of magnesium perchlorate hexahydrate (MPHH) have been reported in the region of internal modes of perchlorate and water. The internal modes reported by Ross are in agreement with our results; however, Miller and Wilkixs results differ to some extent. To the best of our knowledge, the data regarding the bandwidths and intensities in the internal region of water (essential clues to ascertain the coordination effects in the lattices) are available neither for the hydrated nor for the deuterated analogue of MPHH. In the present study, these data are discussed in the light of hydrogen bonding and M—Ow coordination. A simple model is used to estimate the intensity ratio of the v1 and v3 bands of bound water. The mechanical and electrical anharmonities of v2 mode of H2O, HOD, and D2O are also calculated and discussed.

Direct determination by Raman scattering of the conformation of the choline group in phospholipid bilayers.

For clarification of the assignment of the vibrational modes of the choline group, Raman spectra of choline iodides selectively deuterated at three different positions were investigated. The isotope shifts of the C-N stretching vibrations suggested that they are conformation sensitive. When the Raman spectra of choline chloride, carbamoylcholine iodide, carbamoylcholine chloride, and methoxycarbonylcholine iodide are compared with the crystal structures of these compounds, a correlation between the vibrational frequency and the conformation of the O-C-C-N+ backbone could be established. The Raman bands attributed to the "totally" symmetric stretching (v1) and symmetric stretching vibrations (v2) of the C-N bonds of the quaternary ammonium group appeared at about 720 cm-1 and about 870 cm-1, respectively, for the gauche conformation of the O-C-C-N+ backbone, and in the trans conformation, they shifted to about 770 cm-1 (v1) and about 910 cm-1 (v2), respectively. On the basis of this correlation and from measurements of phosphatidylcholine and sphingomyelin bilayers, it was concluded that most of the choline groups in both bilayers take the gauche conformation not only in the solid state but also in the gel and liquid-crystalline states. These data represent the first direct evidence that a gauche conformation for the O-C-C-N+ bond is preferred in the gel and liquid-crystalline states. These key bands, especially the v1 band, are a powerful tool to study the conformation of the choline group in situ not only in the membrane field but also in the neuroscience in connection with acetylcholine.

Resonant coherent transients in a gas in the standing-wave field

Polarization decay in the presence of a standing electromagnetic wave field at a Doppler broadened transition is investigated theoretically and experimentally. It is shown that in the direction opposite to the propagation of an excited pulse the polarization decays at a transition frequency rather than at an exciting field frequency as usual. This permits the use of transients both in studies of relaxation processes and in Doppler-free super-high resolution spectroscopy. A resonant coherent transient has been used in measurements of relaxation decay constants of a dipole moment for collisions in SF6 (λ=10.6μm). This method has enabled one to resolve reliably the structure of theQ(38) transition (λ=10.6μm) of theF 1 0 +E 0=F 2 0 line of the 0→v 3 band in SF6 within a Doppler absorption line.

Observation of spectrally resolved infrared chemiluminescence from vibrationally excited O3(v3)

Infrared emission from the v3 band of ozone near 9.6 μm has been observed in the COCHISE cryogenic chemical reactor/spectrometer. Vibrationally excited O3, formed principally by recombination of O2 with discharge‐produced oxygen atoms at 1 torr and 80–120 K, is expanded into a low‐pressure (∼3 mtorr) environment where its infrared radiation is observed without interference from infrared background effects. The observed spectral distributions are interpreted by using a least squares/spectral synthesis method, in which the vibrational state populations and spectroscopic parameters are adjusted in computed spectra so as to provide the best fits to the observed spectra. The (001) → (000) transition is responsible for most of the observed intensity; however, (Δυ3 = 1) emission from higher vibrational levels is also seen, extending to ∼11 μm (υ3′ ∼ 6). Although the observed spectral distributions are affected by collisional deactivation occurring in the discharge region, the apparent degree of vibrational excitation observed in these experiments should have considerable bearing on investigations of infrared radiation in the upper atmosphere.

Product distributions and isotopic selectivities in ir multiphoton dissociation of pentafluoroiodoethane

Infrared multiphoton dissociation of pentafluoroiodoethane leads to a complex array of reaction products. For photolysis in the v4 band the reaction mechanism involves C2F5—I bond cleavage followed by thermal dissociation of C2F5 radicals. For irradiation within the v3 band at high fluence, efficient secondary photolysis of C2F5 radicals is postulated. At lower fluences the dissociation is isotopically selective leading to C4F10 enriched in carbon-13.

Study of physisorption of carbon dioxide on naa zeolite. Part 1.—Experimental results obtained by infrared spectroscopy

Infrared spectra of CO2 physisorbed on NaA zeolites have been recorded at various temperatures between 178 and 423 K for a constant level of adsorption of ca. 0.5 molecule per cavity. The v3 band profile shows a superposition of two or three bands whose intensities vary with respect to temperature. Preadsorption of water offers better conditions for the observation of bands 2 and 3 owing to the fact that band 1, which is the most intense in the absence of water, is suppressed. We assign the components of the v3 band to different types of adsorption.

Dipole moment of ph3 in v2=1 and v4=1 states by laser stark spectroscopy

Nine transitions belonging to the v4 and v4 bands of PH3 have been brought in resonance with CO2 laser lines, using an intracavity Stark cell. Accurate values of the dipole moments (μv2 = 1 = 0.5740 ±0.0002 D) and of the transition frequencies have been obtained.

Second order Raman spectrum of carbon disulphide in the condensed phase

AbstractBelow 162K, carbon disulphide crystallizes in the space group D2h18 with two molecules in the primitive cell. The internal modes v1, v2 and v3 of the isolated CS2 molecule are split due to static and correlation field splittings. Anderson et al. have extensively studied the Raman and infrared spectra of CS2 at 79 K and 18 K and have analysed the internal and external modes with a lattice dynamical calculation of the q = 0 phonons. However, their spectra reveal the presence of extensive second order features accompanying the v1, v2, v3 and 2v1 bands. The present investigation attempts an interpretation of these second order Raman spectra employing Born's theory and the lattice dynamical calculation of phonons at all allowed q points in the Brillouin zone employing the rigid molecule approximation.

Raman spectrum of the ν2 band of H14N3

AbstractThe rotational‐vibrational Raman Spectrum of the v2 band of H14N3 has been measured. The results of the analysis of the observed wavenumbers are v0 = 2140.308(4) cm−1, ΔB = −0.00312(1) cm−1 and ΔDj = −7(5)×10−9 cm−1. The Q‐branches of the hot band transitions v5→v2+v5 and v6→v2+v6 have been determined to be at 2129.3(1) cm−1.

Evaluation of high resolution IR spectral data using tunable diode lasers

The use of semiconductor tunable diode lasers for the analysis of molecular spectra is discussed with special attention to the determination of accurate spectral parameters.Line identification and band analysis, line intensity and line shape measurements are discussed making use of results obtained in this laboratory in the analysis of NH3 infrared spectra (v2 band). CH4 (v4 band). CF2CI2 (v8 band) and CFCl3.

Identification of the v3 vibration‐rotation band of CF4 in balloon‐borne infrared solar spectra

Infrared solar spectra in the 850 to 1350 cm−1 region, at 0.02 cm−1 resolution, were obtained during a balloon flight made on 27 October 1978 from Alamogordo, New Mexico. Analysis of the 1275–1290 cm−1 region indicates that the atmospheric absorption lines of CH4, N2O, H2O, HNO3 and CO2 near 1283 cm−1 are superimposed on a broader absorption feature which we interpret as due to the v3 band of CF4. Fine structure of CF4 is also identified. Preliminary estimates from the sunset spectra show approximately 75 pptv CF4 near 25 km.

IR Spectroscopy of UF6

Abstract A spectroscopic examination of the IR absorption features of room temperature UF6 has been carried out. We report measurements of the isotope shift for the v3 fundamental band and several binary combination bands; measurements of the absorption coefficient per torr as a function of frequency for the v3 band for both 235UF6 and 238UF6, determination of the frequency dependence of small signal isotope selectivity for the v3 band and binary combination bands, and measurements of the absorption coefficient per torr for the peak absorption of the strong binary combination bands. We both extend the previous measurements of McDowell et al.3 on the IR absorption of room temperature UF6 and agree with their results in cases where repeat measurements are performed.

Raman and infrared band shapes and dynamics of molecular motions for N 2O in solution : v1 and v3 bands in liquid solvents at various temperatures

Raman and infrared band shapes and dynamics of molecular motions for N 2O in solution : v1 and v3 bands in liquid solvents at various temperatures

Line-Shape Parameters in Infrared Bands of Sulfur Dioxide

This paper presents the calculated results for line-shape parameters in the v1 and v3 bands of sulfur dioxide for temperatures between 300 and 1200°K, together with the self-broadening coefficients for some particular rotational lines. The Anderson-Tsao-Curnutte theory was applied to calculate the line half-widths, and a criterion was introduced to determine the line-shape parameters on the basis of a narrow-band model. The calculated results are greatly different from previously assumed values.

Temperature dependence of the IR profile of the v3 band of methane in liquid SF6

Abstract The spectrum of CH4 in liquid SF6 proves particularly interesting as it shows important variations with temperature and, at 40°C, presents a profile similar to the envelope of the gas spectrum. We compare the obtained spectra to those derived from Gordon's collision models by means of a program established by Mc Clung; the best agreement is obtained with model M. The rotation proves important and the mean squared torque opposing the free rotation can be derived from measurement of the moments.

Analysis of the rotational structure of the v5 band of HNO 3 between 891 and 898 cm −1

We present here the analysis of the rotational structure of the v 5 band of HNO 3. Two spectra were used for this study: one recorded with a grille spectrometer by J.P. Chevillard and R. Giraudet and one with a tunable diode laser by P. Brockman, C.H. Bair and F. Allario. This analysis has led to the determination of the band centre and eight rotational constants of the vibrational level υ 5 = 1.

Saturation of the a(6, 0) transition in the v2 band of NH 3 by irradiation with a tea CO 2 laser

Saturation of the a(6, 0) transition in the v2 band of NH 3 by irradiation with a tea CO 2 laser

Coherent anti-Stokes resonance Raman spectroscopy

A description is given of a spectrometer for recording coherent anti-Stokes Raman-scattered signals. The results are reported of an investigation of the v1 (1525 cm–1) band of β-carotene, carried out using this spectrometer.