917～945nm水汽吸收线线强度和空气加宽系数测量

利用连续波窄带可调谐钛宝石激光器和长光程吸收池测量了９１７～９４５ｎｍ６０余条水汽吸收线的强度和空气加宽系数。线强度测量精度优于４％，加宽系数测量精度优于６％。线强度结果和Ｃｈｅｖｉｌａｒｄ等的测量结果比较，比值为０．９８６±０．０６８５，符合得较好。空气加宽系数和Ｈｉｔｒａｎ－９２数据库比较，比值为０．９０６±０．１６４，存在较大的偏差     

Weak Line Water Vapor Spectrum in the 11 787-13 554 cm Region

Long-pathlength Fourier transform spectra of water vapor recorded previously by Schermaul et al. (J. Mole. Spectrosc.211, 169 (2002)) are analyzed in the range 11 787-13 554 cm⁻¹. Wavenumbers, absolute intensities, and self-broadening coefficients, with associated uncertainties, are presented for 2137 lines. Analysis of these lines using variational linelists has been conducted leading to the assignment of 1906 of the new lines to 23 different upper vibrational states in the 3ν+δ, 4ν, and 4ν+δ polyads, a further 19 lines are ascribed to H₂¹⁸O. Comparisons are made with the HITRAN database.     

Weak Line Water Vapor Spectra in the Region 13 200-15 000 cm

New Fourier transform spectra of water vapor are presented in the range 6500-16 400 cm⁻¹ obtained using pathlengths of up to 800 m and long integration times. These spectra have a significantly higher signal-to-noise than previous measurements in this wavenumber range. Wavenumbers, absolute intensities and self-broadening coefficients, all with associated uncertainties, are presented for 3604 lines in the region 13 200-15 000 cm⁻¹. Analysis of these lines using variational linelists, along with other unassigned lines from previous studies, has been conducted. This leads to 952 new line assignments to transitions involving 35 different vibrational states of H₂¹⁶O. A smaller number of lines are assigned to H₂¹⁸O and H₂¹⁷O.     

Diode Laser Spectroscopy of Water Vapor in 1.8 μM: Line Profile Measurements

A diode laser spectrometer has been used for high accuracy H₂O line profile measurements near 5475 cm⁻¹. Measured lineshapes have been least-squares fitted by Voigt profile with a floating Gaussian component. Gaussian component pressure dependence resulting from the Dicke narrowing effect is observed. Line intensities, self- and air-induced broadenings, and shifts of five water vapor lines are presented.     

High-Resolution Infrared Spectra of the OOO Ozone Isotopomer in the Range 900-5000 cm: Line Positions

In pursuing the systematic study of ozone high-resolution infrared spectra, we present here the analysis of line positions of the ¹⁶O¹⁸O¹⁶O isotopomer. The recorded spectra cover the range 900-5000 cm⁻¹, that has allowed 13 bands to be observed: ν₁, ν₃, 2ν₂, ν₂+ν₃, ν₁+ν₂, ν₁+ν₃, ν₁+ν₂+ν₃, 3ν₃, 2ν₁+ν₃, ν₂+3ν₃, ν₁+3ν₃, ν₁+ν₂+3ν₃, and 5ν₃. The analysis of these bands has been performed using effective rovibrational Hamiltonians for 10 polyads of interacting upper vibrational states. To correctly reproduce all observed transitions, it has been necessary to account for resonance perturbations due to “dark” states: (002), (200), (012), (210), (102), (310), (004), (014), (320), (104), and (311). We present the results for spectroscopic parameters (vibrational energy levels, rotational and centrifugal distortion constants, and resonance coupling parameters), as well as the statistics for rovibrational energy levels, range of observed transitions, and typical example of wavefunction mixing coefficients. A comparison of observed band centers with those predicted from an isotopically invariant potential function is discussed. The R.M.S. deviation between predicted and directly observed band centers is ≈0.2 cm⁻¹ up to 2800 cm⁻¹ and ≈0.5 cm⁻¹ for all 13 bands up to 4800 cm⁻¹.     

Extended Analysis of Line Positions and Intensities of Ozone Bands in the 2900-3400 cm Region

The 2900-3400 cm⁻¹ spectral range is revisited for an accurate determination of line positions and line intensities of the 3ν₃, ν₁+2ν₃, 2ν₁+ν₃, and 3ν₁ bands of ozone. The fit on 4520 rotational energy levels of (012), (111), (210), (130), (003), (102), (201), and (300) vibrational states determined from observed transitions of cold and hot bands in the 2400-3400 cm⁻¹ region with J_max=65 and K_{a max}=20 gives a r.m.s.=7×10⁻⁴ cm⁻¹ and provides a satisfactory agreement between calculated and observed line positions (dimensionless standard deviation is χ=1.44). The set of 2580 line intensities of 7 rovibrational bands has been measured and fitted with a r.m.s.=6.9% (χ=1.2), leading to the determination of transition moment parameters for these bands. Using these parameters we have obtained more precise estimation for the integrated band intensities S(3ν₃)=1.41×10⁻¹⁹, S(ν₁+2ν₃)=1.28×10⁻²⁰, S(2ν₁+ν₃)=7.91×10⁻²¹, S(3ν₁)=4.72×10⁻²² cm⁻¹/mol cm⁻² at 296 K, with a cutoff 2×10⁻²⁶ cm⁻¹/mol cm⁻². The interactions of the tetrad (003)/(102)/(201)/(300) with the (130) state and the tetrad (040)/(012)/(111)/(210) are studied.     

Parameters of the Water Vapor Line Contour at Helium Broadening

Optics and Spectroscopy - The method of medium frequencies has been applied to calculate the collisional half-widths of vibrational-rotational lines of a water molecule under helium pressure. The...     

Determination of Integrated Water Vapor and Liquid Water Contents from the Measurements of Microwave Atmospheric Radiation

Radiophysics and Quantum Electronics - We present an overview of the results of our studies in the field of using the radiothermal-detection method for determining the integrated water vapor...     

Measurements of Atmospheric Water Vapor Above Mauna Kea Using an Infrared Radiometer

This paper presents the first results from a prototype infrared radiometer which has been developed to measure variations in atmospheric water vapor column abundance from high altitude sites. The performance of the infrared radiometer is compared and contrasted with that of a water vapor monitor operating at radio frequencies. Analysis shows that the infrared radiometer can measure variations at the level of 1 m precipitable water vapor (pwv) in an integration time of 1 s when the total column abundance is 0.5 mm pwv. Since variations in atmospheric water vapor are the dominant source of phase noise in (sub)millimeter astronomical interferometry, an instrument capable of rapid and high sensitivity water vapor measurements has the potential to provide the necessary phase correction information for interferometric arrays.     

Air- and N(2)-Broadening Parameters of Water Vapor: 604 to 2271 cm(-1)

High-resolution measurements of air- and N(2)-broadened widths and pressure-induced frequency shifts of water vapor were obtained covering the spectral region between 604 and 2271 cm(-1). Over 1300 vibration-rotation transitions were measured including the (000)-(000), (010)-(010), (010)-(000), (020)-(010), and (100)-(010) vibrational bands of H(2)(16)O. Also included were measurements of H(2)(18)O and H(2)(17)O from normal water vapor samples and H(2)(18)O + N(2) observations with oxygen-18-enriched gas samples. Collision-narrowing effects were observed in a few lines involving high J and low K(a) transitions with the lowest measured linewidth coefficient equal to 0.0057(4) cm(-1)/atm (air-broadening) for the completely overlapping transitions, 17 0 17 <-- 18 1 18 and 17 1 17 <-- 18 0 18, at 1235.204 cm(-1). The majority of the linewidth values were derived from the measurements using a Voigt line profile. A few lines with air- or N(2)-broadened half-width values of about 0.012 cm(-1) or less were found to exhibit collision-narrowing effects and were also analyzed with a profile proposed by Galatry. The results are compared to values given in previous studies. Copyright 2000 Academic Press.     

利用傅里叶变换红外光谱技术连续测量环境大气中水汽的稳定同位素

傅里叶变换红外(FTIR)光谱技术可用来测量宽带红外光谱,能同时分析大气中的多种成分。描述了利用开放光路FTIR光谱技术测量环境大气中水汽的稳定同位素的新方法。以分析采集的中红外光谱为基础,在外场实验中,应用开放光程FTIR系统连续测量环境大气中水汽的稳定同位素H216 O和HD16 O,并得到大气中的氘同位素比值δD。对该测量系统,H216 O和HD16 O的测量误差分别约为0.25%和1.60%,氘同位素比值δD的测量精度约为1.32‰。详细分析了其中5天的数据,研究了环境大气中水汽的稳定同位素H216 O、HD16 O以及同位素比值δD随时间的变化规律。并采用Keeling图分析方法,研究了地表蒸散的氘同位素特征。外场实验的结果证明了所提的测量方法和开放光程FTIR系统相结合长期测量环境大气中稳定同位素的能力。     

Effect of Water Vapor Absorption on Measurements of Atmospheric Nitrate Radical by LP-DOAS

利用长程差分吸收光谱技术进行大气NO3自由基测量时,水汽的强烈吸收叠加在测量光谱中,对NO3的精确反演和探测限带来较大的影响. 通过分析水汽吸收的非线性效应,建立了一种去除水汽影响的有效方法. 通过测量日间大气吸收谱,并考虑日间水汽与夜晚水汽变化量,一同参与数据拟合,结果表明该方法可以有效地去除水汽吸收的影响. 把该方法应用于在珠三角外场实验中,获得了好的效果,探测限达到3.6 ppt。     

Rotation Part of the Dielectric Permittivity of Water Vapor for Different Spectral Line Profiles

We estimate the possible influence of spectral line profile (Lorentz profile, Van Vleck–Weisskopf profile, and profile obtained by solving kinetic equation) on the rotation part of the dielectric permittivity of water-vapor monomers. Spectral regions corresponding to long-wavelength (static) and high-frequency (optical) limiting cases as well as regions in close proximity to resonances of various intensities are considered. The studied effects are compared with the corresponding effects on water-vapor absorption coefficient, which are related to factors determining the line-shape structure.     

Line positions and strengths of OCO, OCO and OCO between 2200 and 7000 cm

Line positions and strengths of ¹⁶O¹²C¹⁸O (628), ¹⁸O¹²C¹⁸O (828) and ¹⁷O¹²C¹⁸O (728) were measured between 2200 and 7000 cm⁻¹ using 22 near infrared (NIR) absorption spectra recorded at 0.01-0.013 cm⁻¹ resolution with the McMath-Pierce Fourier transform spectrometer located at the National Solar Observatory on Kitt Peak, Arizona. These data were obtained at room temperature using absorption cells with optical path lengths ranging from 2.4 to 385 m; the cells were filled with natural and ¹⁸O-enriched samples of CO₂ at pressures ranging from 0.54 to 252 torr. The observed line positions were analyzed to obtain the upper state band centers and rotational constants for 17 bands of ¹⁶O¹²C¹⁸O, 19 bands of ¹⁸O¹²C¹⁸O and 8 bands of ¹⁷O¹²C¹⁸O. The majority of the ¹⁸O¹²C¹⁸O and ¹⁷O¹²C¹⁸O bands were measured for the first time. In addition, the rotational constants for the lower states 00001, 01101e and 01101f were derived for all three species using the method of combination differences in which the averaged values obtained from the line positions of two or more bands were least-squares-fitted. Rovibrational parameters were also obtained for the 02201e, 02201f, 10002 and 10001 states of ¹⁸O¹²C¹⁸O. The line position analysis revealed that transitions of the levels 38 ? J′ ? 46 of the 11111f ← 01101f band of ¹⁸O¹²C¹⁸O are perturbed. Perturbed transitions were also observed for the 12212 ← 02201 band and in the high-J transitions (J′ ? 49) of the 20012 ← 00001 band of ¹⁸O¹²C¹⁸O. Band strengths and Herman-Wallis-like F-factor coefficients were determined for 21 bands of ¹⁶O¹²C¹⁸O, 25 bands of ¹⁸O¹²C¹⁸O and 8 bands of ¹⁷O¹²C¹⁸O from least-squares fits to more than 3700 measured transition intensities; band strengths and line positions for 34 of these bands were obtained for the first time.     

Line mixing and speed dependence in CO2 at 6348 cm: Positions, intensities, and air- and self-broadening derived with constrained multispectrum analysis

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.     

Allene nu9 and nu10: Low-Temperature Measurements of Line Intensity

We report laboratory intensity measurements for the weak nu9 (998.8 cm-1) and intense nu10 (841.1 cm-1) bands of allene. Allene is predicted to be a constituent of Titan's atmosphere, and measurements of its abundance would yield important information about the atmospheric chemistry of that body. Spectra were obtained at a temperature of 200 K (approximating Titan conditions) using the high-resolution FTS instrument at Kitt-Peak National Observatory's McMath-Pierce observatory. A total of 505 nu9 and 687 nu10 line intensities were fit using a least-squares method to accurately determine two sets of transition dipole moments. Integrated band intensities computed utilizing the fitted parameters were found to be 36 +/- 4% cm-2 atm-1 and 301 +/- 4% cm-2 atm-1 for nu9 and nu10, respectively, at 200 K. Copyright 1999 Academic Press.     

Neutron-proton charge exchange scattering between 190 MeV and 590 MeV

Differential cross sections of the np charge exchange scattering between 190 MeV and 590 MeV have been measured by detecting the scattered protons in an angular range of 0^° θ_lab 18^°. The cross section at 0^° as well as the logarithmic slope of the angular distribution are found to be almost energy independent, in contrast to previous experiments, but in agreement with recent LAMPF data.