首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
We report on experimental collisional relaxation of the J = 24 ← 23 line of HC314N, located near 218.3 GHz, induced by nitrogen, hydrogen, and helium. The measurements were carried out at selected temperatures in the 235-350 K range using a video-type spectrometer. The foreign gas broadening parameters and their temperature dependences were determined assuming Voigt lineshape profiles and the usual T−n temperature law. The experimental broadening parameters are compared with results derived using the ATC collisional formalism.  相似文献   

2.
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   

3.
Transitions of pure carbon dioxide have been measured using a Fourier transform spectrometer in the 30012 ← 00001 and 30013 ← 00001 vibrational bands. The room temperature spectra, recorded at a resolution of 0.008 cm−1, were analyzed using the Voigt model and a Speed Dependent Voigt line shape model that includes a pressure dependent narrowing parameter. Intensities, self-induced pressure broadening, shifts, and weak line mixing coefficients are determined. The results obtained are consistent with other studies in addition to the theoretically calculated values. Exponential Power Gap (EPG) and Energy Corrected Sudden (ECS) scaling laws were used to calculate the relaxation matrix elements.  相似文献   

4.
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   

5.
The Lamb-dip technique has been applied to the observation of the J = 1 ← 0 transition of DF: for the first time, the hyperfine structure due to D and F have been resolved by using microwave spectroscopy. The high accuracy of this technique allows us to provide hyperfine parameters that are in very good agreement with those obtained from molecular beam experiment. In addition, our frequencies together with the unresolved ones up to J″ value of 47 allow us to provide the most accurate ground state rotational constants of DF known at the moment. Furthermore, due to the presence of a relevant number of strong crossing resonances, the J = 1 ← 0 transition of DF can be considered an illustrative case to show how they modify the shape of Lamb-dip spectra.  相似文献   

6.
The absorption spectra of carbon dioxide (isotope 626, natural abundance in air, ambient temperature) have been studied at total pressures 68-570 Torr with spectral resolution 0.003-0.005 cm−1. The spectra were measured in the spectral domain of 2273-2393 cm−1 by FTIR spectrometer Bruker IFS 125 HR equipped with White-type multipass cell (6.4-41.6 m) and with a cell having 10 cm optical path length. Pressure broadening and shift coefficients were obtained from a series of spectra by means of a nonlinear least-squares spectral fitting technique for the lines of the (00011)←(00001) band with rotational quantum number up to J=82. For fitting of the individual line shapes, we used the Voigt profile with pre-calculated Doppler broadening parameter. The experimental pressure broadening and shift coefficients are compared with the values available in spectroscopic databases HITRAN 2008 and Carbon Dioxide Spectroscopic Databank (CDSD-296) and with other experimental values reported in the literature.  相似文献   

7.
In this work we present a line profile study for air-broadened carbon dioxide transitions in the 30012 ← 00001 and 30013 ← 00001 vibrational bands. The room temperature spectra were recorded at a resolution of 0.008 cm−1 using a Fourier Transform spectrometer. The air-broadening, air-shift, and air-line mixing coefficients were derived from a simultaneous fitting of spectra using the Voigt model and a Speed-Dependent Voigt lineshape model. The results obtained are consistent with other studies in addition to the theoretically calculated values. Exponential Power Gap (EPG) and Energy Corrected Sudden (ECS) scaling laws were used to calculate the relaxation matrix elements.  相似文献   

8.
The collisional relaxation of the J=5←4 rotational transition of CO induced by carbon monoxide, nitrogen, and oxygen has been studied at room temperature. Pressure-broadening parameters were determined as 3.29(2), 2.61(2), and 2.30(2) MHz/Torr for CO, N2, and O2 buffer gases, respectively. Experimental deviations from the Voigt line shape profile have been observed which are mostly the effect of a narrowing in the spectral line core. The difference between the model profile and the experimental profile is less than 0.5% of the maximum line amplitude in the investigated pressure range 0.2-5 Torr. In addition, a small positive collision-induced shift of the line center frequency was observed for the pure gas, corresponding to a pressure self-shift parameter of 6(3) kHz/Torr.  相似文献   

9.
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   

10.
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   

11.
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   

12.
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   

13.
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   

14.
Intensity and line shape parameters which predict spectral lines with absolute accuracies better than 0.3% have been determined for transitions of the 30012 ← 00001 band of 16O12C16O centered near 6348 cm−1 from 26 high resolution, high signal-to-noise ratio spectra recorded at room temperature with the McMath-Pierce Fourier transform spectrometer. To maximize the accuracies of the retrieved parameters, the multispectrum non-linear least squares retrieval technique was modified to adjust the rovibrational constants (G, B, D, etc.) and intensity parameters, including Herman-Wallis terms, rather than retrieving the individual positions and intensities. Speed-dependent Voigt line shapes with line mixing were required to remove systematic errors in the fit residuals. Self- and air-broadening (widths and pressure-induced shifts, speed dependence parameters) and line mixing (off-diagonal relaxation matrix elements) coefficients were thus obtained in the multispectrum fit. Remaining errors were minimized by fitting the weak 30011 ← 00001 band of 16O13C16O as well as the weak hot bands 31112 ← 01101, 32212 ← 02201, 40012 ← 10001, and 40013 ← 10002 of 16O12C16O that contribute interfering absorptions in this spectral window. This study presents the most extensive set of measurements to date for self- and air-broadening and self- and air-shift coefficients of a near infrared band of CO2. This is also the first study where line mixing parameters have been experimentally determined for any parallel CO2 band.  相似文献   

15.
This study provides the first direct experimental measurements of the off-diagonal relaxation matrix element coefficients for line mixing in air-broadened methane spectra for any vibrational band and the first off diagonal relaxation matrix elements associated with line mixing for pure methane in the ν2 + ν3 band of 12CH4. The speed-dependent Voigt profile with line mixing is used with a multispectrum nonlinear least squares curve fitting technique to retrieve the various line parameters from 11 self-broadened and 10 air-broadened spectra simultaneously. The room temperature spectra analyzed in this work are recorded at 0.011 cm−1 resolution with the McMath-Pierce Fourier transform spectrometer located at the National Solar Observatory, Kitt Peak, Arizona. The off-diagonal relaxation matrix element coefficients of ν2 + ν3 transitions between 4410 and 4629 cm−1 are reported for eighteen pairs with upper state J values between 2 and 11. The observed line mixing coefficients for self broadening vary from 0.0019 to 0.0390 cm−1 atm−1 at 296 K. The measured line mixing coefficients for air broadening vary from 0.0005 to 0.0205 cm−1 atm−1 at 296 K.  相似文献   

16.
Using a tunable diode-laser spectrometer, we have measured the O2, N2, air-shift and broadening coefficients for 5 lines of ammonia in the R branch of the ν2 band. These lines are located in the spectral range 1030-1070 cm−1. The pressure shift and broadening are obtained by fitting the measured shapes of these lines by a Voigt profile. The broadening parameters and shift coefficients are compared to the results of theoretical calculations based on the semiclassical Robert-Bonamy formalism (RB) in which the intermolecular potential includes electrostatic, induction, and dispersion energy contributions. The variation of these coefficients with rotational and vibrational quantum numbers is examined. The results are generally in satisfactory agreement with experimental data.  相似文献   

17.
The CO2-broadening coefficients of 24 P- and R-branch transitions in the ν4 + ν5 band of acetylene were measured at room temperature using a diode-laser spectrometer. These lines with J values up to 26, were located in the spectral range 1270 to 1400 cm−1. The collisional broadening coefficients were retrieved by fitting the experimental profiles to the Voigt, Rautian, and Galatry lineshape models. Two experimental values for the narrowing coefficient were determined from the spectra and compared with the theoretical narrowing coefficient. The calculations of these broadenings were also performed in the frame of a semiclassical formalism involving a simple intermolecular potential with an adjustable parameter. The theoretical results are in good agreement with the experimental results and reproduce well the J dependence of the broadening coefficients.  相似文献   

18.
The rotational spectra of the deuterium cyanide isotopic species DCN, D13CN, DC15N, and D13C15N were recorded in the vibrational ground and first excited bending state (v2=1) up to 2 THz. The R-branch transitions from J=3←2 to J=13←12 were measured with sub-Doppler resolution. These very high resolution (∼70 kHz) and precise (±3-10 kHz) saturation dip measurements allowed for resolving the underlying hyperfine structure due to the 14N nucleus in DCN and D13CN for transitions as high as J=10←9. Additional high JR-branch (J=25←24 to J=28←27) transitions around 2 THz and direct l-type (ΔJ=0, J=19 to J=25) transitions from 66 to 118 GHz were recorded in Doppler-limited resolution. For the ground state of D13C15N, the J=1←0 transition was measured for the first time. The transition frequency accuracies for the other deuterated species were significantly improved. These new experimental data, together with the available infrared rovibrational data and previously measured direct l-type transitions, were subjected to a global least squares analysis for each isotopomer. This yielded precise sets of molecular constants for the ground and first excited vibrational states, including the nuclear quadrupole and magnetic spin-rotation coupling constants of the 14N nucleus for DCN and D13CN. The hyperfine structure due to the D, 13C, and 15N nuclei have not been resolved, but led to a broadening of the observed saturation dips.  相似文献   

19.
Pressure-induced foreign-broadening lineshape parameters of the carbon dioxide rovibrational transitions belonging to the (30012)←(00001) overtone band near the 1.573 μm wavelength region are measured by using a tunable diode laser photoacoustic spectrometer. The spectroscopic analysis has concerned the first 11 lines of the R branch. For these lines, the air- and Ar-broadening coefficients are measured at room temperature (∼298 K). The measured broadening coefficients of all the transitions of 12C16O2 are compared with those given in the HITRAN04 database and former measurements with a different spectroscopic method. Agreements and discrepancies are underlined and briefly discussed. The recorded lineshapes are fitted with standard Voigt line profiles in order to determine the collisional broadening coefficient of carbon dioxide transitions.  相似文献   

20.
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   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号