High sensitivity CW-cavity ring down spectroscopy of N2O near 1.5 μm (I)

The absorption spectrum of nitrous oxide, N₂O, in natural isotopic abundance has been recorded by CW-Cavity Ring Down Spectroscopy between 6000 and 6833 cm⁻¹. The spectra were obtained at Doppler limited resolution by using a CW-CRDS spectrometer based on a series of fibered DFB lasers. The typical sensitivity of 2 × 10⁻¹⁰ cm⁻¹, allowed for the detection of lines with intensity as weak as 2 × 10⁻²⁹ cm/molecule while the minimum intensity value provided by HITRAN in the considered spectral region is 2 × 10⁻²⁵ cm/molecule. More than 6000 line positions of five isotopologues contributing to the spectra (¹⁴N₂¹⁶O, ¹⁵N¹⁴N¹⁶O, ¹⁴N¹⁵N¹⁶O, ¹⁴N₂¹⁸O and ¹⁴N₂¹⁷O), were measured with a typical accuracy of 1.5 × 10⁻³ cm⁻¹ and rovibrationally assigned on the basis of their respective global effective Hamiltonian models. Highly excited rovibrational levels corresponding to J values larger than 80 could be detected for the stronger vibrational bands. The band by band analysis led to the determination of the rovibrational parameters of a total of 68 bands, 49 of them being newly reported. The rms value of the deviations of the predictions of the effective Hamiltonian models from the observed line positions is 0.010 cm⁻¹. As expected, the quality of the predictions degrades for the minor isotopologues for which important deviations up to a few wavenumbers were evidenced. Most of the bands were found unperturbed but in a few cases, local rovibrational perturbations were evidenced. The interaction mechanisms and the perturbers were univocally assigned on the basis of the effective Hamiltonian model. In particular, interpolyad couplings were evidenced indicating that the polyad version of the effective Hamiltonian has to be extended to include Coriolis and interpolyad anharmonic interactions.     

High sensitivity CW-Cavity Ring Down Spectroscopy of N2O near 1.5 μm (II)

We present the second part of the investigation of the high sensitivity absorption spectrum of nitrous oxide by CW-Cavity Ring Down Spectroscopy near 1.5 μm. In a first paper [A.W. Liu, S. Kassi, P. Malara, D. Romanini, V.I. Perevalov, S.A. Tashkun, S.M. Hu, A. Campargue, J. Mol. Spectrosc. 244 (2007) 33-47] devoted to the 6000-6833 cm⁻¹ region, more than 6000 line positions of five isotopologues (¹⁴N₂¹⁶O, ¹⁵N¹⁴N¹⁶O, ¹⁴N¹⁵N¹⁶O, ¹⁴N₂¹⁷O, and ¹⁴N₂¹⁸O), were rovibrationally assigned to a total of 68 bands. The achieved noise equivalent absorption (α_min ∼ 2 × 10⁻¹⁰ cm⁻¹) allowed for the detection of lines with intensity weaker than 2 × 10⁻²⁹ cm/molecule. In this contribution, the investigated region was extended down to 5905 cm⁻¹ and additional recordings allowed accessing small spectral sections uncovered in our preceding recordings. A deeper analysis based on the predictions of the effective Hamiltonian model has allowed assigning a total of 3149 transitions and lowering the percentage of lines left unassigned from 51% to 28%. It led to the analysis of 35, 6, 7, and 6 bands for the ¹⁴N₂¹⁶O, ¹⁵N¹⁴N¹⁶O, ¹⁴N¹⁵N¹⁶O, and ¹⁴N₂¹⁸O isotopologues, respectively. Forty-two of these 54 bands are newly observed, while the rotational analysis of the twelve others is significantly extended and improved. Most of the bands were found unperturbed and their line positions could be reproduced within the experimental uncertainty (about 1 × 10⁻³ cm⁻¹). The corresponding spectroscopic parameters are reported. Local rovibrational perturbations induced by either intrapolyad or interpolyad couplings were found to affect five hot bands of ¹⁴N₂¹⁶O. Their detailed analysis is presented.     

15N216O在1650-3450 cm-1的高分辨红外光谱

采用傅里叶变换红外光谱仪记录了富含¹⁵N₂¹⁶O同位素的一氧化二氮样品在1650-3450 cm^-1波段的高分辨振转光谱,得到了该同位素分子超过7300吸收谱线位置的实验值,经分析实验精确度好于5.0×10^-4 cm^-1. 基于有效哈密顿量模型预测和带带转动分析,确定了所有吸收线的归属;获得了29个新吸收带的振转光谱参数,并优化了其他44个吸收带的光谱参数值. 并且发现有效哈     

Global fittings of NNO and NNO vibrational-rotational line positions using the effective Hamiltonian approach

An effective Hamiltonian built up to sixth order in the Amat-Nielsen ordering scheme describing all rovibrational energy levels in the ground electronic state and containing in explicit form all resonance interaction terms due to the approximate relations between harmonic frequencies ω₁≈2ω₂ and ω₃≈4ω₂ was applied to model the observed rovibrational line positions (collected from the literature) of ¹⁴N¹⁵N¹⁶O and ¹⁵N¹⁴N¹⁶O isotopologues of nitrous oxide. For ¹⁴N¹⁵N¹⁶O, 124 effective Hamiltonian parameters were fitted to near 28 000 observed line positions covering the 0.8-8860 cm⁻¹ spectral range. The RMS of the weighted fit is 0.00126 cm⁻¹ and dimensionless standard deviation is 1.48. For ¹⁵N¹⁴N¹⁶O, 121 effective Hamiltonian parameters were fitted to more than 31 000 observed line positions covering the same spectral interval. The RMS of the weighted fit is 0.00185 cm⁻¹ and dimensionless standard deviation is 1.85. In both cases the models describe all available line positions with precision compatible to the measurement uncertainties. A number of local resonance perturbations was found and discussed. Among these perturbations there are interpolyad resonance Coriolis interactions. A comparison of HITRAN-2008 data with the calculations based on the fitted models is presented.     

High sensitivity CW-Cavity Ring Down Spectroscopy of N2O between 6950 and 7653 cm−1 (1.44–1.31 μm): I. Line positions

The absorption spectrum of nitrous oxide, N₂O, has been recorded by CW-Cavity Ring Down Spectroscopy between 6950 and 7653 cm^?1. The spectra were obtained at Doppler limited resolution using a CW-CRDS spectrometer based on a series of fibered DFB laser diodes. The typical noise equivalent absorption, in the order of α_min≈1×10^?10 cm^?1, allowed for the detection of lines with intensity as small as 1×10^–29 cm/molecule.The positions of 7203 lines of four isotopologues (¹⁴N₂¹⁶O, ¹⁴N¹⁵N¹⁶O, ¹⁵N¹⁴N¹⁶O and ¹⁴N₂¹⁸O) were measured with a typical accuracy of 1.0×10^?3 cm^?1. The transitions were rovibrationally assigned on the basis of the global effective Hamiltonian models developed for each isotopologue. The band by band analysis allowed for the determination of the rovibrational parameters of more than 95 bands, most of them being newly reported while new rotational transitions are measured for the others. The measured line positions of the main isotopologue are found to be in good agreement with the predictions of the effective Hamiltonian model but a few deviations up to 0.20 cm^?1 are observed. Local rovibrational perturbations were evidenced for several bands. The interaction mechanisms and the perturbers were univocally assigned on the basis of the effective Hamiltonian models.     

Absolute frequency measurements of the 0002-0000, 2001-0000, and 1201-0000 bands of N2O by heterodyne spectroscopy

The absolute frequencies of 39 lines in the 00⁰2-00⁰0, 20⁰1-00⁰0, and 12⁰1-00⁰0 bands of N₂O in the range 4300–4800 cm^?1 have been measured by heterodyne frequency techniques. The lines were each measured in Doppler-limited absorption, with a color-center laser as a tunable probe of the N₂O and two stabilized CO₂ lasers as reference frequencies. New rovibrational constants have been fitted to these measurements. Tables of calculated transition frequencies are given, with estimated absolute uncertainties as small as 10^?4 cm^?1. The pressure shifts of four lines have been measured, and the values fall within the range of 0 to ?2 MHz/kPa (0 to ?0.2 MHz/Torr).     

Vibration-rotation bands of 15N216O14N218O

The infrared spectrum of 64 bands of the isotopic species ¹⁵N₂¹⁶O of nitrous oxide and of 37 bands of ¹⁴N₂¹⁸O have been analyzed. The studied spectral range extends from 1750 to 6000 cm^?1 for ¹⁵N₂¹⁶O and from 1750 to 3100 cm^?1 for ¹⁴N₂¹⁸O. The effective rotational constants are given for 44 levels of ¹⁵N₂¹⁶O comprising 21Σ, 12Π, 7Δ, 4Φ levels and also for 29 levels of ¹⁴N₂¹⁸O comprising 13Σ, 7Π, 6Δ, 3Φ levels. Thirty-one levels (20Σ, 11Π) of the following isotopic species have also been studied: ¹⁵N₂¹⁷O, ¹⁵N₂¹⁸O, ¹⁴N¹⁵N¹⁸O, ¹⁵N¹⁴N¹⁸O, ¹⁴N₂¹⁷O. In ¹⁵N₂¹⁶O a local Coriolis resonance affects the 10⁰1 level. The “forbidden” Δ-Σ transition 12^2c0-00⁰0 is observed in the spectrum of ¹⁵N₂¹⁶O. The equilibrium values for the internuclear distances have been calculated.     

15N16O的激光磁共振谱与同位素分子15N17O和15N18O的光谱分析

采用内腔式饱和吸收技术获得Lamb凹陷,使CO激光磁共振谱仪的灵敏度及分辨率大大提高.利用该技术对自然丰度下¹⁵N¹⁶O的X²Π(υ=1)←X²Π(υ=0)塞曼跃迁进行测量,实现了包括Λ双分裂在内的各种精细结构的谱分辨.结合已发表的¹⁵NO同位素分子光谱实验数据进行分析计算,拟合得到迄今最完备、最精确的各相关同位素分子¹⁵N^mO(m=16—18)的结构参 关键词：     

High sensitivity CW-cavity ring down spectroscopy of N2O near 1.5 μm (III)

We present the third part of the investigation of the high sensitivity absorption spectrum of nitrous oxide by CW-Cavity Ring Down Spectroscopy near 1.5 μm. In the two first contributions (A. Liu, et al., J. Mol. Spectrosc. 244 (2007) 33-47 and A. Liu, et al., J. Mol. Spectrosc. 244 (2007) 48-62) devoted to the 5905-6833 cm⁻¹ region, more than 9000 line positions of five isotopologues (¹⁴N₂¹⁶O, ¹⁵N¹⁴N¹⁶O, ¹⁴N¹⁵N¹⁶O, ¹⁴N₂¹⁷O and ¹⁴N₂¹⁸O), were rovibrationally assigned to a total of 115 bands, most of them being newly detected. The achieved sensitivity (α_min∼3 × 10⁻¹⁰ cm⁻¹) allowed for the detection of lines with intensity weaker than 2 × 10⁻²⁹ cm/molecule. In this contribution, the investigated region was extended up to 7066 cm⁻¹. The analysis based on the predictions of the effective Hamiltonian model has allowed assigning about 1500 transitions to 17, 1, 2 and 1 bands of the ¹⁴N₂¹⁶O, ¹⁴N¹⁵N¹⁶O, ¹⁵N¹⁴N¹⁶O and ¹⁴N₂¹⁸O isotopologues, respectively. Eleven of these 21 bands are newly reported, while the observations of the transitions are extended to higher J values for most of the others. The band by band analysis has allowed reproducing the measured line positions within the experimental uncertainty (about 1 × 10⁻³ cm⁻¹) and determining the corresponding spectroscopic parameters. A detailed analysis of the rovibrational perturbations affecting three bands of ¹⁴N₂¹⁶O is presented.     

Experimental and ab initio structure of BrN02

Abstract

The ν₂ fundamental bands of different isotopomers of BrN0₂ (⁷⁹Br¹⁵N¹⁶O₂, ⁸¹Br¹⁵N¹⁶O₂, ⁷⁹Br¹⁴N¹⁸O₂, and ⁷⁹Br¹⁴N¹⁶O¹⁸O) located around 13 µm were recorded using highresolution Fourier transform infrared spectrometry. More than 8000 lines of all these isotopomers were reproduced using a Watson-type A-reduced Hamiltonian with a rootmean-square deviation of better than 7×10^?4 cm^?1 for the four isotopomers. Rotational and centrifugal distortion constants for the ν₂=1 states as well as for the vibrational ground states of these isotopomers were determined. For the first time, an analysis of the ground-state rotational constants obtained in this study combined with the constants obtained in our previous work on the ν₂ bands of ⁷⁹Br¹⁴N¹⁶O₂, and ⁸¹Br¹⁴N¹⁶O₂, has allowed us to calculate the r_m, structure of nitryl bromide. The structural parameters obtained were r_m(Br–N)=2.0118(l6) Å, r_m(N–O)=l.l956(12) Å and α(O–N–O)=131.02(12)Å. A new ab initio structure of nitryl bromide calculated at the CCSD(T)/SDBaug-cc-pVQZ level of theory is presented and was found to be in fair agreement with the experimental structure.     

Far infrared spectral lines and absorptance calculation of NO

The positions and intensities of pure rotation lines of ¹⁴N¹⁶O have been calculated between 10–200 cm^-1 and are tabulated. The line by line absorption spectrum has been computed using tabulated parameters, and compared with experimental spectra measured by other authors. The spectral emission of atmospheric NO has been calculated for an altitude of 14.5 km, where some measurements have been carried out. After comparing the NO and the background H₂O+O₂+O₃ spectra, it is shown that the NO emission in the far i.r. spectrum of the lower stratosphere is negligible.     

Improved rovibrational constants and frequency tables for the normal laser bands of 12C16O2

New frequency difference measurements between Doppler-free stabilized laser lines in the 9.4- and 10.4-μm bands of ¹²C¹⁶O₂, including high-J and across-the-band-center measurements, have made significant improvements in the rovibrational constants. The absolute frequencies were referred to the methane stabilized 3.39-μm HeNe laser. Frequency tables generated from these constants have absolute uncertainties of less than two parts in 10¹⁰ and are about a factor of 10 better than older tables. In addition, the laser lines P_I(50) in ¹³C¹⁶O₂ and R_II(26) in ¹³C¹⁸O₂, which were used as reference lines in recent visible laser frequency measurements, were also measured to about the same accuracy.     

Rotational structure of the 000, 010, 100, 020, and 001 vibrational states of the D216O molecule: Spectroscopic assignment of rotational levels up to J, Ka = 30 and analysis of published data

The complete spectroscopic assignment of calculated Partridge-Schwenke rotational energy levels up to J, K _a = 30 is presented for the 000, 010, 100, 020, and 001 vibrational states of the D₂ ¹⁶O molecule. The nonpolynomial model of an effective rotational Hamiltonian is used to perform the assignment and to analyze the experimental energy levels available in the literature for these states. The results obtained are compared with the data calculated by other authors. The results of this study can be useful in searching for and identifying new, highly excited rotational levels of D₂ ¹⁶O, as well as in creating the databases of parameters of rovibrational transitions of the water molecule.     

N2Broadening in theCO 2–0 Band around 4167 cm

N₂broadening coefficients have been measured for 65 lines of the¹³C¹⁶O 2–0 band using a Fourier transform spectrometer. These lines are located in the spectral range 4011–4252 cm⁻¹. The spectra were recorded with 99% isotopically pure¹³CO in a White-type cell at a resolution of 0.005 cm⁻¹. Voigt profiles convolved with the FTS apparatus function were fitted to the experimental lineshapes using a nonlinear least-squares fit technique. From the fits the Lorentzian HWHM was determined as function of N₂pressure. Pressure broadening coefficients formbetween −33 and +34 were obtained with uncertainties of 5.8%. The results are compared to earlier published N₂broadening coefficients and our measurements in the 2–0 band of¹²C¹⁶O. To our knowledge this is the first investigation of¹³CO pressure broadening.     

Vibration-rotation bands of 14N15N16O15N14N16O: 1.6–5.7 μm region

The infrared Fourier spectrum of 63 bands of ¹⁴N¹⁵N¹⁶O and of 69 bands of ¹⁵N¹⁴N¹⁶O have been measured and analyzed from 1750 to 6000 cm^?1. The rotational constants are given for 20 Σ, 11 Π, 7 Δ, and 3 Φ levels of ¹⁴N¹⁵N¹⁶O and 21 Σ, 14 Π, 8 Δ, and 5 Φ levels of ¹⁵N¹⁴N¹⁶O. Two bands of the previously unreported isotopic species ¹⁴N¹⁵N¹⁷O and ¹⁵N¹⁴N¹⁷O have been observed. Several local resonances are present in the levels 31^1c0 and 04⁰1 in ¹⁴N¹⁵N¹⁶O; 10⁰1, 06⁰0, 11^1d1, 12⁰1 in ¹⁵N¹⁴N¹⁶O. In both isotopes two “forbidden” Δ-Σ transitions are observed: 04^2c0-00⁰0 and 12^2c0-00⁰0.     

The high resolution infrared spectrum and laser Stark spectroscopy of thev8 band of propyne

The perpendicularv ₈ band lying in the 1000–1100 cm^–1 region has been studied from infrared and laser Stark, spectra. We were interested in the part of spectrum corresponding to the spectral range of the 9 m CO₂ laser lines. Assignments of rovibrational lines with J'<40 and K'<6 have been made. About 100 Stark resonances have been assigned to 12 rovibrational transitions. Effective molecular constants and dipole moment have been determined with high accuracy. A list of close resonances with CO₂ laser lines is given and may be used for optical pumping experiments.     

Vibration-rotation bands of nitrous oxide: 4.1 micron region

The infrared spectrum of nitrous oxide has been measured and analyzed from 2265 cm^?1 to 2615 cm^?1. Newly refined effective rotational constants for twenty-one vibrational states of ¹⁴N₂O, three vibrational states each of ¹⁴N₂¹⁸O and ¹⁵N¹⁴N¹⁶O, two states of ¹⁴N¹⁵N¹⁶O and one state of ¹⁴N₂¹⁷O have been calculated.The most interesting features observed are two Δ-Σ “forbidden” bands, 04^2c0-00⁰0 and 12^2c0-00⁰0. These bands occur because of Coriolis interaction between unperturbed vibrational states having l = 0 and l = 2.     

Vibration-rotation spectrum of N2O in the region of the lowest fundamental ν2

The high resolution infrared spectrum of N₂O in the region of ν₂ has been studied with a Fourier transform spectrometer at a resolution of (about) 0.005 cm^?1 and an accuracy of about ±0.00005 cm^?1. In addition to ν₂, “hot” bands associated with this band and the bending fundamental ν₂ of ¹⁵N¹⁴N¹⁶O and ¹⁴N¹⁵N¹⁶O were analyzed.     

N2O同位素的紫外光解：同位素分馏和产物的转动量子态分布

采用时间依赖的量子波包法研究¹⁴N¹⁴N¹⁶O、¹⁴N¹⁵N¹⁶O、¹⁵N¹⁴N¹⁶O、¹⁵N¹⁵N¹⁶O、¹⁴N¹⁴N¹⁷O和¹⁴N^{14相似文献}   

Fourier transform measurements of water vapor line parameters in the 4200-6600 cm region

New high-resolution water vapor absorption spectra were obtained at room temperature in the 4200-6600 cm⁻¹ spectral region by combining Fourier transform spectrometers (FTS) with single and multiple reflection cells. With absorption paths from 0.3 to 1800 m in pure and air diluted water vapor, accurate measurements of about 10400 lines in an intensity range from 10⁻²⁹ to 10⁻¹⁹ cm/molecule have been performed. Positions, intensities, self- and air-broadening coefficients and air-induced shifts were determined for the H₂¹⁶O, H₂¹⁷O, H₂¹⁸O and HDO isotopologues. The rovibrational assignment of the observed lines was performed with the use of global variational predictions and allowed the identification of several new energy levels. One major contribution of this work consists of the identification of 3280 new weak lines. A very close agreement between the new measured parameters and those listed in the database is reported as well as between the observations and the most recent variational calculations for the positions and the intensities. The present parameters provide an extended and homogeneous data set for water vapor, which is shown to significantly improve the databases for atmospheric applications, especially in the transmission windows on both sides of the band centered at 5400 cm⁻¹.