共查询到20条相似文献,搜索用时 0 毫秒
1.
Jean-Marcel Colmont François Rohart Jean-Pierre Bouanich 《Journal of Molecular Spectroscopy》2006,238(1):98-107
Extensive experiments on the K = 3 component of the J = 12-11 rotational transition of acetonitrile CH3C14N, located near 220.7 GHz, were performed at different temperatures in the range 235-350 K. They allow determining the N2-, H2-, and He-broadening coefficients, as well as their temperature dependences. More specific measurements on all the K-components of the involved transition perturbed by N2 at 303 K allow to point out a clear decreasing of the broadening coefficient with increasing K. Narrowing effects are clearly observed, and experimental lines were analysed both with Voigt and speed dependent Voigt profiles; but no exhaustive lineshape study was carried out. All the experimental parameters are compared with results derived from a semiclassical calculation of collisional interactions, including electrostatic, induction, and dispersion energy contributions. 相似文献
2.
Jean-Marcel Colmont Linh Nguyen François Rohart 《Journal of Molecular Spectroscopy》2007,246(1):86-97
Collisional relaxation has been considered for millimeter lines of carbon monoxide at room temperature. Accurate measurements of carbon dioxide- and rare gases-broadened widths have been performed on the J = 3 ← 2 rotational line of 12CO by using a video-type spectrometer. Measurements of nitrogen-, oxygen-, and xenon-broadened widths of the J = 5 ← 4 rotational line of 13CO were also carried by using a frequency-modulated spectrometer. A lineshape study performed on all the investigated binary systems provide confirmation that Voigt profile is not a suitable model to analyse experimental lines in the millimeter-waves region. On one hand, using this profile in the low pressure range, i.e. in the Doppler regime, the retrieved collisional linewidths do not follow a linear variation with the perturbing gas pressure. On the other hand, regardless of the pressure, lineshapes exhibit a narrowed profile. An accurate analysis of the pressure dependence of relaxation rates show that the Galatry profile is not appropriate and that experimental lineshapes are actually Speed Dependent Voigt profiles. Accurate broadening parameters were retrieved from this profile and compared to previous reported values and predictions calculated from the Robert-Bonamy formalism. Finally a variation of the ratio of relaxation speed dependence to broadening parameters versus relative masses of the collision partners is presented. 相似文献
3.
For the purpose of atmospheric applications, we have measured N2- and O2-induced broadenings and shapes of rotational lines of N2O in the 235-350 K temperature range, precisely the J=8←7, J=22←21, and J=23←22 lines, located near 201, 552, and 577 GHz, respectively. The analysis of experimental lineshapes shows up significant deviations from the Voigt profile, which are characteristic of line narrowing processes. In a first step, the Voigt profile was considered for the determination of pressure broadening parameters and of their temperature dependencies. Results are in good agreement with the dependence from rotational quantum number previously observed for other rotational and rovibrational lines. They are well explained by calculations based on a semiclassical formalism that includes the atom-atom Lennard-Jones potential in addition to electrostatic interactions up to hexadecapolar contributions. In a second step, observed lineshapes were analyzed by using the Galatry profile and a speed-dependent Voigt profile. The nonlinear pressure behavior observed for the diffusion rate β involved in the Galatry profile leads to rule out the possible role of velocity/speed changing collisions, and to infer that discrepancies from the Voigt profile result from the dependence of relaxation rates on molecular speeds. This interpretation is supported by the comparison of optical and kinetic radii and confirmed by theoretical calculations of relaxation rates. Finally, it can be claimed that, for the N2O-N2 and N2O-O2 systems, deviations from the Voigt profile are explained by a speed-dependent Voigt profile. 相似文献
4.
The 0310 ← 0110 parallel Q branch of N2O has been studied at 297 K and over the pressure range 1-130 torr. Absorption spectra were recorded using a high resolution (1.5 MHz or 5 × 10−5 cm−1) and high signal-to-noise (>3500:1) mid-infrared spectrometer based on difference-frequency infrared generation in AgGaS2. In the low-pressure range (1-11 torr) we obtained accurate values for the line strengths, the broadening coefficients, the weak mixing coefficients, and the overall shifting of the branch. The medium pressure results, ranging from 23 to 130 torr, were analyzed by treating the band as a whole, using a relaxation matrix formalism, based on an energy gap scaling law. We find, effectively, that only 36% of the rotationally inelastic collisions are associated with Q branch mixing, the rest presumably being associated with Q-P and Q-R mixing in the same vibrational band. The pressure shifting coefficient of the 0310 ← 0110 Q branch as a whole was also determined and found to be 5.8 × 10−3 cm−1/atm towards lower frequencies. 相似文献
5.
The N2- and O2-broadening effect have been investigated for 10 absorption lines of the CO2 (3001)III ← (0000) band centered at 6231 cm−1, in the range from P(28) to R(28) by a near-infrared diode-laser spectrometer. We have analyzed the observed line profiles with the Galatry function, and determined the N2- and O2-broadening coefficients precisely. The air-broadening coefficients for these lines have been derived. The present results are compared with those of the previous studies for this band and with some of the other bands. 相似文献
6.
We report the first infrared spectra of pure gaseous cyanobutadiyne between 400 and 4000 cm−1. A great care has been taken to obtain a pure sample so that, for the first time, intensities could be determined for all the main bands in the studied domain. The results are compared with available theoretical works. A sample containing a mixture of HC5N and DC5N was also studied in the same wavenumber range. The data obtained in this study should be very useful to identify those compounds by IR spectroscopy and will allow the quantification of cyanobutadyine in various environments. 相似文献
7.
V. Malathy Devi A. Predoi-Cross M.A.H. Smith A.W. Mantz 《Journal of Molecular Spectroscopy》2004,228(2):580-592
Room temperature values for self-broadened and hydrogen-broadened Lorentz halfwidth coefficients, and self and hydrogen pressure-induced shift coefficients have been measured for transitions with rotational quantum number m ranging between −24 and 24 in the 2 ← 0 band of 12C16O. The spectra were recorded with the McMath-Pierce Fourier transform spectrometer located at the National Solar Observatory on Kitt Peak. The analysis was performed using a multispectrum nonlinear least squares technique. We have compared our results with similar measurements published recently. 相似文献
8.
Temperature dependence of pressure broadening of the N = 1− fine structure oxygen line at 118.75 GHz
M.Yu. Tretyakov M.A. Koshelev I.A. Koval V.V. Parshin L.M. Kukin L.I. Fedoseev Yu.A. Dryagin A.F. Andriyanov 《Journal of Molecular Spectroscopy》2007,241(1):109-111
The absorption profile of the N = 1− fine structure line of oxygen was recorded by a resonator spectrometer at a frequency range of 110-130 GHz at atmospheric pressure and different temperatures ranging from −21 °C up to +22 °C. Analysis of the observed line shape allowed determination of the temperature dependence of the line pressure broadening. The measured value of the temperature exponent is n = 0.74(5) for self-broadening. Consistency of the measurements is supported by simultaneous measurements of the line intensity, the line mixing parameter and the line center frequency, and by comparison of obtained values with previously known data. 相似文献
9.
Hejie Li Aamir Farooq Jay B. Jeffries Ronald K. Hanson 《Journal of Quantitative Spectroscopy & Radiative Transfer》2008,109(1):132-143
High-resolution absorption lineshapes of two H2O transitions near 7185.60 and 7154.35 cm−1 have been recorded in a heated static cell as a function of temperature (296-1100 K) and pressure (6-830 Torr) using two distributed-feedback diode lasers. The measured absorption spectra are least squares fit to both Voigt and Galatry profiles. Strong collisional-narrowing effects are observed in the Ar-broadened H2O spectra at near-atmospheric pressure due to the relatively weak collisional broadening induced by Ar-H2O collisions, while collisional narrowing is not significant for pure H2O absorption lineshapes. Line strengths and self-broadening coefficients are inferred from the pure H2O absorption spectra and compared with published data. Temperature dependences of the Ar-induced broadening, narrowing, and shift coefficients are determined using Galatry fits to the absorption data. The measured collisional-narrowing parameters have similar temperature dependence to the collisional-broadening coefficients. 相似文献
10.
The pure rotational J + 1 ← J transitions, with J = 0, 1, 3-8, of H13CN have been observed in the millimeter- and submillimeter-wave region using the Lamb-dip technique to resolve the hyperfine structure due to H, 13C, and 14N. The present observations allow us to provide for the first time the spin-rotation constant of 13C and the spin-spin interaction constant S12 (between H and 13C) as well as to remarkably improve the quadrupole coupling and spin-rotation constants of 14N. In addition, a good empirical estimation of CI(H), based on ab initio calculations, has also been provided. Furthermore, our frequencies together with previous data permit to determine the most accurate ground state rotational parameters known up to now. 相似文献
11.
Using a high-resolution tunable diode laser photoacoustic spectrometer, self-, N2 and O2 pressure broadening coefficients for the first 11 transitions of 12C16O2 in the R branch of the (30012) ← (00001) overtone band at the 6348 cm−1 have been revisited at room temperature (∼298 K). Air-broadening parameters have also been calculated from the N2 and O2 measurements. The dependence of the broadening on rotational quantum number m is discussed. The recorded lineshapes are fitted with standard Voigt line profiles in order to determine the collisional broadening coefficients of carbon dioxide transitions. The results are compared to our previous measurements and to the values reported in the HITRAN04 database and by other research group with a different spectroscopic technique. 相似文献
12.
C. Degli Esposti L. Bizzocchi P. Botschwina K.M.T. Yamada G. Winnewisser S. Thorwirth P. Frster 《Journal of Molecular Spectroscopy》2005,230(2):162-195
The rotational spectrum of HC5N has been investigated in the millimeter-wave region, from 60 to 290 GHz, for 15 vibrationally excited states which lie approximately between 500 and 860 cm−1, namely (v6 v7 v8 v9 v10 v11) = (000005), (000006), (000007), (000008), (000020), (000030), (001000), (010000), (100000), (000021), (000101), (001001), (010001), (000110), and (001010). Gas-phase copyrolysis of pyridine and phosphorus trichloride or, alternatively, a dc discharge in a gaseous mixture of vinyl cyanide and acetylene were used to produce the semi-stable HC5N molecule. A large number of vibrational and rovibrational interactions has been taken into account to fit properly the measured transition frequencies of the states investigated. The most important perturbations are caused by the high-order Coriolis resonances observed between the (v8, v10) and (v8 − 1, v10 + 2) states, and between the (v7, v10, v11) and (v7 − 1, v10 + 3, v11 − 1) states, and by the cubic anharmonic interactions which mix the (v6, v8, v11) states with the (v6 − 1, v8 + 1, v11 + 1) states, and the (v6, v10) states with the (v6 − 1, v10 + 2) states. The analysis of the spectra was facilitated by CCSD(T) calculations with the cc-pVQZ basis, which provided accurate predictions of a large variety of spectroscopic constants like harmonic vibrational wavenumbers, vibration–rotation coupling constants, l-type doubling constants, and normal-coordinate cubic force constants. Excellent agreement between experiment and theory was generally observed, even when the experimental data were strongly perturbed by resonance effects. 相似文献
13.
Jean-Marcel Colmont Bilal Bakri François Rohart Georges Wlodarczak 《Journal of Molecular Spectroscopy》2003,220(1):52-57
We report on linewidth measurements on the J=24K,11−23K′,10 and J=38K,33−37K′,32 millimeter wave transitions in the ground vibrational state of nitric acid, located near 470.23 and 544.36 GHz, respectively. Experiments were performed with N2 and O2 as perturber molecules, in the 240-350 K temperature range by using a video-type spectrometer. The foreign-gas broadening parameters and their temperature dependence coefficients were determined using the Voigt profile, no narrowing effect being observed. In order to check the reliability of reported values, we carried out measurements on the J=14K,12−13K′,11 transition located near 206.6 GHz, previously observed in two other laboratories. For this last line all the reported values are consistent themselves within one claimed standard deviation. 相似文献
14.
Cyanobutadiyne has been produced by gas phase copyrolysis of pyridine and phosphorus trichloride in a flow reactor. The yield of the reaction is sufficiently good to allow the detection of rotational transitions of the 13C and 15N containing species in natural abundance. Normal pyridine and its fully deuterated variant have been used as precursors, making it possible to study the ground-state rotational spectra of 14 isotopomers in the millimeter wave region. Very accurate values of the rotational and quartic centrifugal distortion constants have been obtained for all the isotopic species investigated, and in addition the sextic distortion constant has been precisely determined for the most abundant variants H12C514N and D12C514N, for which the measurements have been extended up to 460 GHz. A mixed experimental-theoretical equilibrium structure has been evaluated for cyanobutadiyne combining experimental ground-state rotational constants with theoretically computed zero-point contributions. The re geometry is compared with operationally defined purely experimental structures, namely r0, rs, and rm(1) molecular structures. 相似文献
15.
P.M. Shirage K. Kihou K. Miyazawa C.H. Lee H. Kito Y. Yoshida H. Eisaki Y. Tanaka A. Iyo 《Physica C: Superconductivity and its Applications》2010,470(20):986-988
We report the iron isotope effect on a transition temperature (Tc) in an optimally-doped (Ba,K)Fe2As2 (Tc = 38 K) and SmFeAsO1−y (Tc = 54 K) superconductors. In order to obtain the reliable isotope shift in Tc, twin samples with different iron isotope mass are synthesized in the same conditions (simultaneously) under high-pressure. We have found that (Ba,K)Fe2As2 shows an inverse iron isotope effect αFe = −0.18 ± 0.03 while SmFeAsO1−y shows a small iron isotope effect αFe = −0.02 ± 0.01, where the isotope exponent α is defined by Tc ∼ M−α (M is the isotopic mass). The results show that αFe changes in the iron-based superconductors depending on the system. The distinct iron isotope effects imply the exotic coupling mechanism in the iron-based superconductors. 相似文献
16.
Line position, intensity and line shape parameters (Lorentz widths, pressure shifts, line mixing, speed dependence) are reported for transitions of the 30013 ← 00001 band of 16O12C16O (ν0 = 6227.9 cm−1). The results are determined from 26 high-resolution, high signal-to-noise ratio spectra recorded at room temperature with the McMath-Pierce Fourier transform spectrometer. To minimize the systematic errors of the retrieved parameters, we constrained the multispectrum nonlinear least squares retrieval technique to use quantum mechanical expressions for the rovibrational energies and intensities rather than retrieving the individual positions and intensities line by line. Self- and air-broadened Lorentz width and pressure-induced shift, speed dependence and line mixing (off-diagonal relaxation matrix elements) coefficients were adjusted individually. Errors were further reduced by simultaneously fitting the interfering absorptions from the weak 30012 ← 00001 band of 16O13C16O as well as the weak hot bands 31113 ← 01101, 32213 ← 02201, 40014 ← 10002 and 40013 ← 10001 of 16O12C16O in this spectral window. This study complements our previous work on line mixing and speed dependence in the 30012 ← 00001 band (ν0 = 6347.8 cm−1) [V.M. Devi, D.C. Benner, L.R. Brown, C.E. Miller, R.A. Toth, J. Mol. Spectrosc. 242 (2007) 90-117] and provides key data needed to improve atmospheric remote sensing of CO2. 相似文献
17.
Line profiles of the J = 1-0 transition of the hydrogen chloride, H35Cl and H37Cl isotopomers, were measured with a BWO-based submillimeter-wave spectrometer at AIST in real form: three hyperfine transitions for each isotopomer, i.e., total six lines at 625 and 626 GHz. The effect of foreign gases on the broadening and shift was determined for N2, O2, and Ar. The modified Voigt function was applied as the line shape function for preliminary analysis, where the collisional-narrowing effect was clearly observed. In the final analysis, we applied the Galatry function and determined the integral intensity, line center position, Lorentzian width, and contraction parameter for each absorption line. The magnitudes of the foreign-gas pressure-broadening coefficients decrease in order of N2, O2, and Ar. The line-shift coefficients were clearly observed, the magnitudes of which decrease in order of Ar, O2, and N2. The pressure dependence of contraction parameter was determined, although with poor precision. 相似文献
18.
The structures and energetics of the chemisorbed CO2, CHx species and H as well as C2H4 on the α-Mo2C(0 0 0 1) surface have been computed at the GGA-RPBE level of density functional theory. It is found that CO2 adsorbs dissociately into CO and O, in agreement with the experimental finding. The adsorbed O, CHx and H species prefer the site of three surface molybdenum atoms over a second layer carbon atom (VC site). On the basis of the calculated adsorption energies of CHx and H, the sequential dehydrogenation of CH4 and the C/C coupling reaction of CHx have been discussed. 相似文献
19.
The ground state rotational spectrum of the 14NF3 and 15NF3 isotopic species of nitrogen fluoride has been observed in the ∼450-810 GHz frequency range. This investigation allowed us to improve the rotational parameters for both isotopologues. In particular, for the first time the K = 3 line splitting parameter and the sextic centrifugal distortion constants have been determined for 15NF3. 相似文献
20.
Fusakazu Matsushima Nobuhiro Tomatsu Takashi Nagai Yoshiki Moriwaki Kojiro Takagi 《Journal of Molecular Spectroscopy》2006,235(2):190-195
Frequencies of pure rotational transitions in the v2 = 1 vibrationally excited state of H216O were measured with a tunable far-infrared spectrometer in the frequency range of 0.5-5 THz. Molecular parameters of Watson’s A-reduced Hamiltonian have been obtained to reproduce the observed frequencies. 相似文献