High-resolution stimulated Raman spectroscopy and analysis of v2 and v3 bands of 13C2H4 using the D2h top data system

HRMS 2015, Dijon, France, August 24-28, 2015Peer Reviewe

High resolution infrared and Raman spectra of 13C12CD2: The CD stretching fundamentals and associated combination and hot bands

11 pags.; 4 figs.; 9 tabs.© 2015 AIP Publishing LLC. Infrared and Raman spectra of mono 13C fully deuterated acetylene, 13C12CD2, have been recorded and analysed to obtain detailed information on the C—D stretching fundamentals and associated combination, overtone, and hot bands. Infrared spectra were recorded at an instrumental resolution ranging between 0.006 and 0.01 cm−1 in the region 1800–7800 cm−1. Sixty new bands involving the ν 1 and ν 3 C—D stretching modes also associated with the ν 4 and ν 5 bending vibrations have been observed and analysed. In total, 5881 transitions have been assigned in the investigated spectral region. In addition, the Q branch of the ν 1 fundamental was recorded using inverse Raman spectroscopy, with an instrumental resolution of about 0.003 cm−1. The transitions relative to each stretching mode, i.e., the fundamental band, its first overtone, and associated hot and combination bands involving bending states with υ 4 + υ 5 up to 2 were fitted simultaneously. The usual Hamiltonian appropriate to a linear molecule, including vibration and rotation l-type and the Darling–Dennison interaction between υ 4 = 2 and υ 5 = 2 levels associated with the stretching states, was adopted for the analysis. The standard deviation for each global fit is ≤0.0004 cm−1, of the same order of magnitude of the measurement precision. Slightly improved parameters for the bending and the ν 2 manifold have been also determined. Precise values of spectroscopic parameters deperturbed from the resonance interactions have been obtained. They provide quantitative information on the anharmonic character of the potential energy surface, which can be useful, in addition to those reported in the literature, for the determination of a general anharmonic force field for the molecule. Finally, the obtained values of the Darling–Dennison constants can be valuable for understanding energy flows between independent vibrations.The Bologna authors acknowledge the Università di Bologna and the financial support of the Ministero dell’ Istruzione dell’Università e della Ricerca (PRIN 2012 “Spettroscopia e Tecniche computazionali per la ricerca Astrofisica, atmosferica e Radioastronomica”). D.B. and R.Z.M. acknowledge the financial support of the Ministry of Economy and Competitiveness through Research Grant No. FIS2012-38175.Peer Reviewe

An Experimental and Theoretical Study of Nitrogen-Broadened Acetylene Lines

We present experimental nitrogen-broadening coefficients derived from Voigt profiles of isotropic Raman Q-lines measured in the 2 band of acetylene (C2H2) at 150 K and 298 K, and compare them to theoretical values obtained through calculations that were carried out specifically for this work. Namely, full classical calculations based on Gordon's approach, two kinds of semi-classical calculations based on Robert Bonamy method as well as full quantum dynamical calculations were performed. All the computations employed exactly the same ab initio potential energy surface for the C2H2N2 system which is, to our knowledge, the most realistic, accurate and up-to-date one. The resulting calculated collisional half-widths are in good agreement with the experimental ones only for the full classical and quantum dynamical methods. In addition, we have performed similar calculations for IR absorption lines and compared the results to bibliographic values. Results obtained with the full classical method are again in good agreement with the available room temperature experimental data. The quantum dynamical close-coupling calculations are too time consuming to provide a complete set of values and therefore have been performed only for the R(0) line of C2H2. The broadening coefficient obtained for this line at 173 K and 297 K also compares quite well with the available experimental data. The traditional Robert Bonamy semi-classical formalism, however, strongly overestimates the values of half-width for both Qand R-lines. The refined semi-classical Robert Bonamy method, first proposed for the calculations of pressure broadening coefficients of isotropic Raman lines, is also used for IR lines. By using this improved model that takes into account effects from line coupling, the calculated semi-classical widths are significantly reduced and closer to the measured ones

Microalgae as a safe food source for animals: nutritional characteristics of the acidophilic microalga Coccomyxa onubensis

Background Edible microalgae are marine or fresh water mesophilic species. Although the harvesting of microalgae offers an abundance of opportunities to the food and pharmaceutical industries, the possibility to use extremophilic microalgae as a food source for animals is not well-documented. Objective We studied the effects of dietary supplementation of a powdered form of the acidophilic microalga Coccomyxa onubensis on growth and health parameters of laboratory rats. Method Four randomly organized groups of rats (n=6) were fed a standard diet (Diet 1, control) or with a diet in which 0.4% (Diet 2), 1.25% (Diet 3), or 6.25% (Diet 4) (w/w) of the standard diet weight was substituted with dried microalgae powder, respectively. The four groups of animals were provided ad libitum access to feed for 45 days. Results C. onubensis biomass is rich in protein (44.60% of dry weight) and dietary fiber (15.73%), and has a moderate carbohydrate content (24.8%) and a low lipid content (5.4%) in which polyunsaturated fatty acids represent 65% of the total fatty acid. Nucleic acids are present at 4.8%. No significant difference was found in growth rates or feed efficiency ratios of the four groups of rats. Histological studies of liver and kidney tissue revealed healthy organs in control and C. onubensis-fed animals, while plasma hematological and biochemical parameters were within healthy ranges for all animals. Furthermore, animals fed a microalgae-enriched diet exhibited a statistically significant decrease in both blood cholesterol and triglyceride levels. The blood triglyceride content and very low density lipoprotein-cholesterol levels decreased by about 50% in rats fed Diet 4. Conclusions These data suggest that C. onubensis may be useful as a food supplement for laboratory animals and may also serve as a nutraceutical in functional foods. In addition, microalgae powder-supplemented diets exerted a significant hypocholesterolemic and hypotriglyceridemic effect in animals

Experimental and theoretical study of line mixing in methane spectra. IV. Influence of the temperature and of the band

The infrared bands line-mixing effects of methane perturbed by nitrogen were discussed at different pressures. The spectral shapes of the ν2, ν4 and ν3 bands were compared at room temperature while the ν3 region was employed for the investigation of thermal effects. The effects of collisions in the ν4 region's spectra were calculated at the room temperature. The Coriolis coupling between ν2 and ν4 vibrational states resulted in the failure of evolution modeling with increasing pressure of absorption.© 2000 American Institute of PhysicsPeer Reviewe

Anharmonic potential functions as derived from Raman intensities: Methane

7 pags., 2 figs., 5 tabs.The cubic force field of methane has been investigated on the basis of the analysis of Raman scattering cross sections of binary overtones and combination bands. Seven absolute cross sections, ten symmetry cubic force constants, and the second derivative of the mean CH bond polarizability are the original results of present work. Some of these cubic force constants are determined with high accuracy. Most Ĥ22 rovibrational constants calculated by means of present anharmonic force field are in good agreement with the experimental values reported by various authors. © 1984 American Institute of Physics.We are indebted to J. Brandmiiller and H. W. Schrotter for moral support and to the Stiftung Volkswagenwerk of the Federal Republic of Germany for providing the high power laser source to obtain some of the results presented here

Measurement of V-V vibrational relaxation rates in ortho-para collisions in N2 at 77K by double resonance stimulated Raman spectroscopy

Poster presented at the High Resolution Molecular Spectroscopy Conference held in Budapest (Hungary) on August 25-30, 2013. More details at the conference web site: http://lmsd.chem.elte.hu/hrms/index.html.Peer Reviewe

Electro-optical parameters and Raman intensities of CH4, CH3D, CH2D2, CHD3 and CD4

The absolute Raman intensities and the depolarization ratios of the vibrational bands of gaseous CH4, CH3D, CH2D2, CHDS and CD4 have been computed here using a compact formulation of the bond polarizability theory, in its zero and first-order approximations. The agreement with experimental values taken from the literature is very good for the first-order approximation, although the difference between both approximations is not very large for these molecules. The derivatives of the polarizability with respect to the symmetry coordinates of methane are given with signs that are physically meaningful. © 1976 Taylor & Francis Group, LLC.Peer reviewe

Medida de ensanchamientos colisionales en la rama Q del espectro Raman estimulado de 14N2 inducidos mediante colisiones con H2

Las Palmas de Gran Canaria, 4-9 Julio, 2004REN2002-01618/CLIN

Direct determination of state-to-state rotational energy transfer rate constants via a Raman-Raman double resonance technique: ortho-acetylene in v2=1 at 155 K

12 pages, 6 figures, 4 tables.- PACS nrs: 33.20.Sn, 33.15.Mt, 33.20.Fb, 33.40.+f, 33.20.Tp, 33.80.Wz.A new technique for the direct determination of state-to-state rotational energy transfer rate constants in the gas phase is presented. It is based on two sequential stimulated Raman processes: the first one prepares the sample in a single rotational state of an excited vibrational level, and the second one, using the high resolution quasi-continuous stimulated Raman-loss technique, monitors the transfer of population to other rotational states of the same vibrational level as a function of the delay between the pump and the probe stages. The technique is applied to the odd-J rotational states of v2 = 1 acetylene at 155 K. The experimental layout, data acquisition, retrieval procedures, and numerical treatment are described. The quantity and quality of the data are high enough to allow a direct determination of the state-to-state rate constant matrix from a fit of the experimental data, with the only conditions of detailed balance and of a closed number of states. The matrix obtained from this direct fit is also compared with those obtained using some common fitting and scaling laws.This work has been funded by the Spanish Ministry of Education and Science through research Grant No. FIS2005-02029.Peer reviewe