Tunable diode laser measurements of the band strength and collision halfwidths of nitric oxide

The strength of the fundamental absorption band of nitric oxide at 5.3 μm and collision halfwidths of nitric oxide lines broadened by nitrogen, argon, and combustion gases were measured in absorption cell, flat flame and shock tube experiments using a tunable diode laser. Room temperature absorption measurements were made in an absorption cell filled with NO/N₂ or NO/Ar mixtures or with probe-extracted combustion gases. High temperature (to 2500 K) absorption measurements were performed for NO in N₂ and NO in Ar using a shock tube, and for NO in combustion gases using a flat flame burner.Absorption measurements were made on lines from 1860–1925 cm^?1, ($\text{Ω=}\text{1}\text{2}$ and $\text{3}\text{2}$,P($\text{5}\text{2}$-R ($\text{29}\text{2}$)) resulting in a band strength of 123±8 cm^-2 atm^?1 at 273.2 K. Collision halfwidth dependencies for each broadening species were examined as a function of rotational quantum number and temperature.     

Stratospheric temperature profile from balloon-borne measurements of the 10.4-μm band of CO2

The technique of nonlinear least squares spectral curve fitting has been used to derive the stratospheric vertical temperature profile from balloon-borne measurements of the 10.4-μm band of CO₂. The spectral data were obtained at sunset with the ?0.02 cm^-1 resolution University of Denver interferometer system from a float altitude of 33.5 km near Alamogordo, New Mexico, on 23 March 1981. The r.m.s. deviation between the retrieved temperature profile and correlative radiosonde measurements is 2.2 K.     

Line Intensities in the ν6Band of CH3F at 8.5 μm

Infrared absolute line intensities of the ν₆band of CH₃F have been measured around 8.5 μm using a diode-laser spectrometer. These line strengths were obtained by the equivalent width method and, for 13 lines, by fitting a Rautian profile to the measured shape of the lines. From these results, we have deduced the vibrational band strength to beS⁰_v= 9.66 ± 0.13 cm⁻²atm⁻¹at 296 K and the first Herman–Wallis factors.     

Measurement of N2O line strengths from high-resolution Fourier transform spectra

The absolute line strengths in four bands of nitrous oxide N₂O have been measured by means of the high information Fourier transform interferometer at the Laboratoire d'Infrarouge (apodized resolution: 5.4 × 10^?3 cm^?1). The investigated transitions were the 2ν₁ and ν₁ + 2ν₂ near 4 μm, and the ν₁ and 2ν₂ near 8 μm, which are all used for atmospheric detection. Conditions for extracting accurate line parameters are discussed. Reproducibility of measurements is better than 3% while absolute precision on both line and band intensities is shown to be currently better than 5%. Band intensity values compare well with the most recent determinations whereas the line strengths were never measured previously.     

Diode laser line strength measurements of the (ν4 + ν5)0 band of 12C2H2

A diode laser spectrometer that was operated in sweep integration mode was used to measure individual line strengths for 17 R-branch transitions of the (ν₄ + ν₅)⁰ combination band of ¹²C₂H₂ at 7.4 μm. Analysis of these results gives a band strength S_v = 64.4 ± 2.0 cm^?2 atm^?1 at 296 K. Line-broadening parameters for several of these transitions were determined by using both N₂ and He as broadening gases.     

Diode laser measurements of the band strengths of ν3 and ν6 in 12CH3D

A diode laser spectrometer has been used to measure line strengths for 143 transitions in the ν₆ fundamental band of ¹²CH₃D near 9 μm. These line-strength measurements have been used to derive a band strength for ν₆ and ν₃. The band strength derived for ν₆ is 61.7 ± 1.8 cm^?2 atm^?1, and that for ν₃ is 49.3 ± 1.4 cm^?2 atm^?1 at 395 K.     

Absolute Line Intensities in the 2ν3Band of16O12C32S

The strengths of 100 lines in the 2ν₃band of¹⁶O¹²C³²S have been measured at high resolution in the spectral range 4069–4118 cm⁻¹, using a tunable difference-frequency laser spectrometer. These intensities were obtained by fitting Voigt profiles to the measured shapes of the lines. The vibrational transition moment [(2.141 ± 0.020) × 10⁻²D] and the absolute intensity (16.19 ± 0.24 cm⁻²atm⁻¹at 296 K) of the 2ν₃band of¹⁶O¹²C³²S are determined from these linestrength measurements.     

Measurement of the transition strength of the 00o2 9.4 μm sequence band in CO2 using a tunable diode laser

We report the first accurate measurements of the transition strengths and linewidths of the 00^o2 9.4 μm sequence lines of CO₂. This sequence band is found to be very similar to the regular 00^o1 laser band, except for an experimentally determined factor of 1.89±0.12 increase in transition strength (if the CO₂ molecule is treated as a simple harmonic oscillator the theoretical increase in transition strength is 2.0). The laser absorption spectrometer used for these measurements can detect absorption coefficients in CO₂ of ≈10⁻⁷ m⁻¹, and we discuss the feasibility of using this sensitivity to monitor rare isotopic forms of CO₂. Work supported by the Department of National Health and Welfare, Environment Canada, Ontario Ministry of the Environment, and Atmospheric Environment Service, Environment Canada.     

基于差频中红外激光的痕量气体高分辨光谱检测研究

研究了基于差频光源的高分辨中红外激光光谱检测系统,差频中红外光源使用两台近红外半导体激光器作为种子光源,采用PPLN晶体作为非线性混频器件,结合准相位匹配技术实现了3.2~3.7 μm中红外相干光源输出,最大差频输出功率约为1 μW.以CH₄为例检验了系统的高分辨红外光谱检测特性,选择CH₄分子3 028.751 cm^-1 v₃基频吸收线作为分析谱线,10 cm光程的检测限为0.8 ppm.光谱数据分析表明,系统检测限主要受到标准具光学噪音的限制.     

Temperature dependence of intensities of the 8–12 μm bands of CFCl3

The absolute intensities of the 8–12 μm bands from freon 11 (CFCl₃) were measured at temperatures of 294 and 216°K. Intensities of the bands centered at 798, 847, 934, and 1082 cm^-1 are all observed to depend on temperature. The temperature dependence for the 847 and 1082 cm^-1 fundamental regions is attributed to underlying hot bands; for the ν₂ + ν₅ combination band (934 cm^-1), the observed temperature dependence is in close agreement with theoretical prediction. The implication of these results on atmospheric i.r. remote-sensing is briefly discussed.     

Measurements of the electronic transition moment of the A2Π−X2Π system of ClO

The electronic transition moment of the A²Π?X²Π band system of ClO has been determined from spectral emission measurements behind incident shock waves in Cl₂-O₂ mixtures. The temperature of the radiating gas was typically 3500°K. Narrow bandpass radiometers were used to obtain absolute measurements of the ClO emission from which electronic transition moments were derived by a synthetic spectrum analysis. Absolute measurements of the O₂ Schumann-Runge system and the photo-dissociation cross section of ClO are also reported.     

A line parameter list for the ν2 and ν4 bands of 12CH4 and 13CH4, extended to J′ = 25 and its application to planetary atmospheres

Line parameters (transition frequencies, line strengths, line widths, ground state energies and quantum identifications) for the ν₂ and ν₄ bands of ¹²CH₄ and ¹³CH₄ have been calculated for J'?25 using the simultaneous coupled fitting procedure of Gray and Robiette. Molecular constants for the ν₂ band of ¹³CH₄ were estimated from isotopic shifts from ¹²CH₄ values. Agreement with laboratory spectra, where available, is always well within 1 cm^-1 over the entire spectral range covered by the list. The most serious problem in comparison with laboratory data is the omission of lines belonging to “hot” bands in this spectral region. This list is valuable in remote sensing problems for sorting out lines of trace species from weak methane lines and for determining the atmospheric opacity in relatively transparent spectral regions. Applications of the parameter list are demonstrated for remote sounding of the Jovian atmosphere. The list is available on magnetic tape from the authors.     

The temperature-dependent absorption spectrum of the v3 band of SF6 at 10·6 μm

Mixtures of SF₆ diluted by argon were heated behind an incident shock front in the range 400 to 1500K. Absorption measurements at 11 wavelengths near 10·6 μm were made on the post-shock, equilibrated gas using a CO₂ laser. A band contour model, which makes use of known spectroscopic constantd and the experimental results, satisfactorily accounts for the observed temperature dependence of the absorption coefficient. We are able to estimate the identity of the transitions responsible for absorption of the laser radiation.     

Comparison of band model and integrated line-by-line synthetic spectra for methane in the 2.3 μm region

The 2.3 μm spectral region of methane can be used to retrieve cloud properties of planetary spectra, provided parameters for the methane spectrum are known. Two standard techniques for calculating absorption spectra in this region are compared here. A Voigt profile Mayer-Goody random band model is applied, using coefficients empirically fitted by Fink et al. to CH₄ spectra recorded with high absorping amounts at 10 cm^?1 resolution. Calculation of the absorption is also done with a line-by-line direct integration method for the same gas conditions using molecular parameters obtained by combining an older unpublished list of observed positions and estimated line strengths (derived from 0.04 cm^?1 resolution data) with quantum assignments from the literature. The molecular parameters have been evaluated for the 4180–4590 cm^?1 region by comparing new laboratory spectra with 0.01 cm^?1 resolution recorded at 296 and 153K with synthetic spectra calculated at the same conditions. The deficiencies of the molecular parameters and random band coefficients for this spectral region of CH₄ are then discussed qualitatively and demonstrated by comparing 10 cm^?1 resolution synthetic spectra calculated by both methods for the same gas conditions at 296, 153, and 55 K.Curves of growth of the total equivalent width are calculated at 296 and 55K for a pathlength of 50 cm and pressures up to 10 atm. Changing the mean line spacing in the band model gives better agreement between the spectra calculated by the two techniques at low gas temperatures. The required multiplier has been determined for the mean line spacing for pressures from 10^?6 to 10^?1 atm at 55, 100, and 150 K.     

Determination of the oscillator strengths of Sn(I) in the ultraviolet (2400–4000 Å)

The emission spectrum of Sn(I) generated in a direct current arc plasma (Ar-SnCl₄ mixture) has been studied. The relative socillator strengths were obtained in the u.v. spectral range (2400–4000 Å) from measurements of branching ratios and from the study of radial temperature distribution and radial emission coefficients obtained by side-on measurement. These relative oscillator strengths were converted to an absolute scale by using as reference the lifetime determination of the ³P₁⁰ state. The results are compared with other absolute measurements.     

Some studies of BF2 and B+F implanted Silicon

Ion-implanted shallow junctions have been investigated using BE₂ (molecular ions) by the anodic oxidation method coupled with a four-point probe technique. BF₂ ions were implanted through screen oxide at doses of 3–5 × 10¹⁵ ions/cm² and energies of 25 and 45 keV which is equivalent to 5.6 keV and 10 keV of boron ions. The effect of energy, dose and annealing temperature on shallow junctions is presented in this paper. The shallow junctions in the range of 0.19 μm to 0.47 μm were fabricated.

The effect of fluorine on sheet resistivity of boron implanted silicon at various doses, treated with two-step and three-step annealing, is also presented for comparison in the paper.     

Multi-band infrared CO2 absorption sensor for sensitive temperature and species measurements in high-temperature gases

A continuous-wave laser absorption diagnostic, based on the infrared CO₂ bands near 4.2 and 2.7 μm, was developed for sensitive temperature and concentration measurements in high-temperature gas systems using fixed-wavelength methods. Transitions in the respective R-branches of both the fundamental υ ₃ band (~2,350 cm^?1) and combination υ ₁ + υ ₃ band (~3,610 cm^?1) were chosen based on absorption line-strength, spectral isolation, and temperature sensitivity. The R(76) line near 2,390.52 cm^?1 was selected for sensitive CO₂ concentration measurements, and a detection limit of <5 ppm was achieved in shock tube kinetics experiments (~1,300 K). A cross-band, two-line thermometry technique was also established utilizing the R(96) line near 2,395.14 cm^?1, paired with the R(28) line near 3,633.08 cm^?1. This combination yields high temperature sensitivity (ΔE” = 3,305 cm^-1) and expanded range compared with previous intra-band CO₂ sensors. Thermometry performance was validated in a shock tube over a range of temperatures (600–1,800 K) important for combustion. Measured temperature accuracy was demonstrated to be better than 1 % over the entire range of conditions, with a standard error of ~0.5 % and µs temporal resolution.     

Shock-tube measurements of the f-number for the fundamental vibration-rotation bands of AlO in the X2∑+ electronic ground-state

An i.r. filter-radiometer was used to measure the absorption f-number for the fundamental vibration-rotation band system belonging to the X²∑⁺ electronic ground-state of AlO. The measurements were conducted with gas-mixtures containing initially (AlBr₃)₂ in O₂ and Ar by monitoring the i.r. emission around 905 cm^-1 behind reflected shockwaves at temperatures between 3540 and 4056°K and at total pressures between 1·55 and 2·09 atm. The observed optical densities ranged from 2·49 × 10^-2to5·16 × 10^-2 cm-atm and the absolute emission-intensity data were determined with an effective spectral bandwidth of 18·68 cm^-1 under optically-thin conditions. The observation of time-invariant emission signals together with the result that the derived f-number data did not show systematic variations for large changes in the test conditions were taken as proof that local thermodynamic equilibrium was reached. The average over all of the data obtained resulted in an absorption f-number of f₀ = (3·32 ± 0·66) × 10^-5 for the (0, 1)-band of the system, corresponding to an integrated band-intensity of α₀₁ = 724 ± 145 atm^-1 -cm^-2 at 298°K.Particular care was taken in order to establish the desired gas compositions behind the reflected shock-waves by using a dynamic mixing procedure at elevated temperatures together with a heated shock-tube test section. The consistency of the measurement procedures was established by demonstrating that the final f-value determinations were independent of the following systematic variations in the experimental techniques and parameters: changes in the initial mole-concentrations of (AlBr₃)₂ produced by temperature changes of the heat-bath used for establishing an equilibrium source for (AlBr₃)₂-vapor; changes in the flow rate of the O₂:Ar gas mixture through the (AlBr₃)₂-powder sample; changes in the time used for flushing the shock-tube test section with the (AlBr₃)₂: O₂: Ar test-gas mixtures; large changes in the concentrations of the dominant chemical species in order to rule out the possibility of contributions by other radiators to the AlO i.r. emission observed at LTE behind the reflected shock waves.     

Line strengths of the ν1 + ν4 band of 12CH4

The line strengths of the ν₁ + ν₄ band of ¹²CH₄ at 4223.5 cm^?1 were measured using a leastsquares procedure that iterates between the observed spectrum and a synthetic spectrum calculated at correct instrumental and gas sample conditions. The methane spectrum was recorded at 0.011 cm^?1 resolution with signal-to-noise ratios of 300 to 1 or better using a Fourier transform spectrometer at Kitt Peak National Observatory. Line assignments were evaluated and extended to upper state J of 13. The observed line strengths reflect significant perturbation by other states so that only portions of the band can be used to determine a band strength of 6.92 (2) cm^?2 atm^?1 at 296 K with a Herman-Wallis factor of (1 – 0.0035(2)m)².     

Line parameters for the 01111-00001 band of COO from SOIR measurements of the Venus atmosphere

CO₂ is the major constituent of the atmosphere of Venus. Absorption lines due to its ¹²C¹⁶O¹⁸O isotopologue have been observed for the first time in Venus spectra in the 2930-3015 cm⁻¹ spectral region, where the HITRAN database does not contain any line from this isotopologue. The measurements were performed by the SOIR instrument, which is part of the SPICAV/SOIR instrument on board the Venus Express mission of ESA. SOIR measured the atmospheric transmission of the upper atmosphere of Venus (z>70 km) by performing a solar occultation experiment using the atmosphere as a gigantic absorption cell. The identification of this newly observed band was first made recently from Mars atmosphere observations by US colleagues. We have made independent theoretical calculations of the positions of the lines of this new 01111-00001 absorption band, which coincide perfectly with the positions of the observed lines. Assuming an oxygen isotopic ratio similar to the one measured previously in the lower atmosphere of Venus, the line strengths of each observed line are deduced and listed.