Rotation-vibration spectrum of CH3F in the range 2000–2100 cm−1

The spectrum of CH₃F between 2000 and 2100 cm^?1 has been investigated under high resolution (0.025 cm^?1). Three parallel bands have been analyzed: 2ν₃ of ¹²CH₃F for which the rotational K structure has been studied, 3ν₃-ν₃ of ¹²CH₃F, and 2ν₃ of ¹³CH₃F. The band center of the main band 2ν₃ of ¹²CH₃F has been found at 2081.383 cm^?1.     

Intensity measurements in freon bands of atmospheric interest

The absolute intensities of the i.r. absorption bands, which are located in the atmospheric window region, of CFCl₃ (“Freon-11”) and CF₂Cl₂ (“Freon-12”) have been measured at 300°K. Our best estimates for these parameters are: for CFCl₃ (“Freon-11”), S_v = 635±36 cm^-2atm^-1 (9.2μ band), S_v = 1536±45 cm^-2atm^-1 (11.8μ band); for CF₂Cl₂ (“Freon-12”), S_v = 718±14 cm^-2atm^-1 (8.7μ band), S_v = 1136±22 cm^-2atm^-1 (9.1μ band), and S_v = 1302±40 cm^-2atm^-1 (10.9μ band).     

Intensities and widths of H2O lines between 1800 and 2100 cm-1

A non-linear, least-squares program was used to obtain the line intensities and widths of 91 air-broadened lines in the ν₂ rotation-vibration band of water vapor in the region from 1800 to 2100 cm^-1. The values obtained for the line intensities are, on the average, about 7% stronger than the Air Force Cambridge Research Laboratories (AFCRL) Atmospheric Absorption Line Parameters Compilation. The experimental values for the half widths of the H₂O lines are, on the average, 4% higher than the calculated AFCRL values. The measurements have confirmed the narrow widths of some high J transition lines measured by tunable diode laser spectroscopy.     

Wavenumbers,line strengths,and assignments in the Doppler-limited spectrum of formaldehyde from 2700 to 3000 cm−1

The spectrum of H₂CO from 2700 to 3000 cm^?1 has been examined at Doppler-limited resolution using a tunable difference frequency laser spectrometer at Lincoln Laboratory. The wavenumbers and strengths of 4350 absorptions have been determined with an accuracy of 0.001 cm^?1 and 5%, respectively. These data have been incorporated into the analysis of lower-resolution data from Florida State University to assign 72% of the observed absorptions to one of seven bands: ν₃ +ν₄ (a C-type band at 2655 cm^?1), ν₃ + ν₆ (a B-type band at 2719.156 cm^?1), ν₁ (an A-type band at 2782.457 cm^?1), ν₅ (a B-type band at 2843.326 cm^?1), ν₂ + ν₄ (a C-type band at 2905 cm^?1), 2ν₃ (an A-type band at 2999.5 cm^?1) and ν₂ + ν₆ (a B-type band at 3000.066 cm^?1). The band ν₃ + ν₄ has been observed for the first time, and the band center for 2ν₃ has been corrected from a value of 2972 cm^?1 to the value listed above. The effects of strong Fermi and Coriolis resonances on the spectra are discussed.     

Intensity measurements in the v4-fundamental of methane

The absolute intensities of all the J-multiplets between R(13) at 1375cm^-1 and P(12) at 1225 cm^-1, in the v₄-fundamental of ¹²CH₄, have been measured at 300°K. Our values are consistent with published band-intensity measurements and also with the theoretical line strength tabulation by Fox. Spectral transmittance computation using a Lorentz line shape with a hydrogen-broadened half-width of 0.075 cm^-1 atm^-1 at 300°K for all the lines in the band is in excellent agreement with our experimental data measured with a spectral resolution of 0.2 cm^-1. Our best estimate for the absolute intensity of the band is 145±8 cm^-2 atm^-1 at STP.     

Magnon Raman scattering in CoBr2

The one-magnon Raman spectrum of CoBr₂ has been investigated as a function of temperature, and peak frequency, integrated intensity and width parameters obtained. The results obtained for the band energy at low temperature (22.2 ± 0.2 cm^-1 at 5.7.K) are in good agreement with AFMR and neutron scattering results. The one-magnon energy renormalises relatively slowly with increasing temperature and is about 15 cm^-1 at T_N = 19 K, whereas the integrated intensity approaches zero like the magnetization at T_N and the width diverges. A low intensity band at 26.8 ± 1 cm^-1 (7.6K) may be due to two-magnon scattering from spin waves along the c-axis.     

Tunable diode laser measurements of spectral parameters of HCN at room temperature

A tunable infrared diode laser was used to record 17 fully resolved vibration-rotation transitions in the v₁ fundamental band of HCN at 3μ. The experiments were conducted in an absorption cell on room temperature mixtures of HCN diluted by N₂ and Ar. The v₁ fundamental band strength of HCN was determined to be 267±8 cm^-2 atm^-1 at 273.2 K. Small but significant reductions in the residual errors were obtained by using the Galatry profile rather than the Voigt profile to fit the experimentally recorded line shapes. Collisional broadening and narrowing parameters were determined simultaneously from Galatry profile fits to the data. The collision-broadened linewidths of HCN lines in N₂ and Ar were determined as a function of rotational quantum number of transitions ranging from P(14) to R(14) (3268.22-3353.29 cm^-1). The optical diffusion coefficients of HCN in N₂ and Ar at 300 K were determined from the collisional narrowing parameters and were 0.074±0.01 and 0.016±0.03 cm²s^-1 respectively.     

Far-infrared reflectivity of indium doped Pb1−xSnxTe

We have measured, as a function of temperature, the reflectivity from 40 to 240 cm^-1 of films of Pb_1?xSn_xTe grown from sources with x = .21 and .25 on BaF₂ substrates. In the x = .21 sample the plasma reflectivity minimum abruptly shifts from 110 cm^-1 to 190 cm^-1 as the temperature is lowered from 40 to 8 K. This shift corresponds to large changes in DC transport behavior that have been attributed to the indium level entering the band at about 40 K. Fits of the reflectivity to a classical two-oscillator (plasmon-phonon) model give values for the carrier plasma frequency which are in excellent agreement with values that can be calculated from DC Hall measurements with a two-band model for the carrier effective mass.     

High-resolution stimulated Raman gain spectrum of the ν1 band of SF6

We report rotationally resolved stimulated Raman gain spectra of the ν₁ band of SF₆. The fundamental band exhibits a rigid-rotor type spectrum that is readily fit with a band origin of Δα = 774.5445 and a single rotational term Δβ = ?1.10376 × 10^?4 cm^?1. We also observed and analyzed the ν₁ + ν₆ hotband with band origin at 774.1820 cm^?1. With an experimental resolution of 0.0024 cm^?1 there is no evidence for centrifugal distortion or tensor splitting in either band, although the ν₁ + ν₆ band does exhibit first-order Coriolis splitting as expected.     

Absolute intensities and pressure broadening coefficients measured at different temperatures for the 201II ← 000 band of 12C16O2 at 4978cm-1

Absolute line intensities and self-broadening coefficients have been measured at 197° and 294°K for the 201_II ← 000 band of ¹²C¹⁶O₂ at about 4978cm^-1. The vibration-rotation factor (F_VR), the purely vibrational transition moment (∣R(O)∣), and the integrated band intensity (S_band) are deduced from the measurements. The results are: F_VR(m)=1+(0.24±0.08)x10^-4m+(0.55+0.21)x10^-4m², ∣R(O)∣= (4.340±0.008x10^-3 debye, S_band=96372±190cm^-1km^-1atm^-1_STP. The results for self-broadening coefficients, as well as for individual vibration-rotation lines, are presented in the text.     

Measurements of the HCN ν3 band broadened by N2

N₂-broadened halfwidths have been measured for 51 absorption lines belonging to the ν₃ fundamental band of hydrogen cyanide (¹H¹²C¹⁴N) near 3311 cm^?1. The data were recorded at room temperature using a Fourier transform spectrometer with a nominal resolution of 0.06 cm^?1. A nonlinear least-squares spectral-fitting procedure was used to obtain both line intensities and collision-broadened halfwidths from scans recorded at several different pressures. The N₂-broadened halfwidths, determined for all lines with J ≤ 25 in both the P and R branches of the band, show the expected distribution with J for broadening by a nonpolar gas. The halfwidth values range from approximately 0.17 cm^?1 atm^?1 near the band center to 0.11 cm^?1 atm^?1 for high-J lines. The band intensity for the ν₃ fundamental derived from these measurements is 236.2 ± 9.5 cm^?2 atm^?1 at 296 K, and empirical coefficients for the vibration-rotation interaction F-factor were also determined.     

Strengths and air-broadened widths of H2O lines in the 2950–3400 cm-1 region

Measurements of the strengths and air-broadened widths of 223 lines of water vapor have been made with high resolution in the region 2950–3400 cm^-1. The strength data of the lines in the 2ν₂ and ν₁ bands are analyzed to determine the band strengths and the coefficients of the F factors. The band strengths of the 2ν₂ and ν₁ bands were found to be 1.75±0.08 and 10.3±1.1 cm^-2 atm^-1 at 296 K, respectively. The selection rules of the lines observed in the ν₃ band are forbidden in the symmetric-rotor limit. The majority of the measured strengths of these lines differ from the calculated values because of different asymmetries in the upper and lower vibrational states. Also, Coriolis perturbations in several lines of the ν₁ and ν₃ bands were observed in the strength measurements. The direct method was applied to determine the air-broadened line widths. The results are compared to the computed values of Benedict and Kaplan. There is good agreement between this work and the computed results for line width values greater than 0.05 cm^-1 atm^-1. However, for line widths less than 0.05 cm^-1 atm^-1, the measured values are smaller than the computed widths. A value of 0.018 cm^-1 atm^-1 is given for the width of the line at 3378.071 cm^-1, whereas the calculated value is 0.032 cm^-1 atm.     

High resolution measurements of the line positions and strengths of the 2ν2 band of H2CO

Spectra of the 2ν₂ band of formaldehyde have been obtained with high resolution (0.035 cm^?1). Measurements were made with path lengths of 8, 16, and 24 m and at sample pressures from 0.1 to 0.3 mm Hg at room temperature (～296°K). From these data, the following constants were determined for the 2ν₂ band in wavenumber units: v₀=3471.718±0.004,A=9.3958±030013,B=1.28100±0.00024,C=1.11662±0.00024, Tbbb=-12.8±0.5×10^-6,Taabb=60±5×10^-6. The line strengths were also obtained from the data. The strengths were analyzed to determine the band strength and the rotational factors. At 296°K, the strength of the 2ν₂ band was found to be 15.5 ± 0.9 cm^?1/(cm·atm).     

Diode laser measurements of line strengths and collisional half-widths in the ν1 band of OCS at 298 and 200K

Absolute line strengths and self-broadened half-widths have been measured at 298 and 200 K for spectral lines ranging from J = 1 to 55 in the ν₁ band (860 cm^-1) of ¹⁶O¹²C³²S, using a tunable diode laser spectrometer. The vibrational transition moment (6.412 ± 0.16 × 10^-2D) as well as the absolute intensity (29.63±1.48 cm^-2-atm^-1 at 298 K), of the ν₁ band are determined from these line-strenght measurements. By applying two semi-classical impact theories of collisional broadening, we have obtained results for half-widths at 298 and 200 K which are significantly larger than the experimental data for |m|<50. However, the variation of the linewidths with temperature is well reproduced theoretically.     

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.     

Vapor phase infrared spectrum of CF3Cl in the region 4.8–16 μm

The gas phase infrared spectrum of CF₃Cl was studied at medium resolution in the range 2100-600 cm^?1. A high number of bands including fundamental, overtone, combination, and “hot” bands of the two species, CF₃³⁵Cl and CF₃³⁷Cl, with natural isotopic abundance, was identified. The frequency values of the two long-wavelength fundamentals, ν₃ and ν₆, were evaluated with higher accuracy by differences of suitable combination and “hot” bands. The Q-branch rotational structure of the ν₂ + ν₅ perpendicular band for the main variety was analyzed and the molecular constants obtained are reported.     

High-resolution infrared spectrum of CH2D2: The ν3 fundamental band at 7 μm

The infrared spectrum of CH₂D₂ has been recorded in the region of 1345 to 1561 cm^?1 with a resolution of 0.030 to 0.026 cm^?1. Most of the observed lines have been assigned to transitions of the ν₃ band of CH₂D₂. However, 114 lines have been identified as transitions of the ν₂ band of H₂¹⁶O whose band origin has been directly determined to be 1594.7472 ± 0.0030 cm^?1. A few weak lines, probably belonging to the ν₅ fundamental of CH₂D₂, remain unassigned. The band center ν = 1435.1326 ± 0.0030 cm^?1 and a set of upper state constants were obtained for the ν₃ band of CH₂D₂. Although a slight perturbation was noticed in the ν₃ band, all wavenumbers have been fitted with a standard deviation of 3.8 × 10^?3 cm^?1.     

First analysis of the ν5 band of DNO3 (deuterated nitric acid) in the 11 μm region

The infrared spectrum of DNO₃ (deuterated nitric acid) was recorded at high resolution (0.0027 cm⁻¹) in the 700-1400 cm⁻¹ region on a Bruker IFS 120 HR Fourier transform spectrometer. The analysis of the ν₅ band of DNO₃ centred at 887.657 cm^-1 which is mostly an A-type band, was performed making use of the ground state parameters achieved by Drouin et al. [Drouin BJ, Miller CE, Fry JL, Petkie DT, Helminger P, Medvedev IR. J Mol Spectrosc 2006;236:29-34]. The ν₅ fundamental band is strongly perturbed because of the existence of the ν₇+ν₉ dark combination band at 882.21  cm^-1. The 5¹ and 7¹9¹ energy levels of DNO₃ are coupled through A and B type Coriolis resonances, and as a consequence, numerous lines from the ν₇+ν₉ dark combination band could be identified also. In this way about 1070 and 75 energy levels of the 5¹ and 7¹9¹ vibrational states, respectively, were satisfactorily reproduced by the energy levels calculation which account for the observed resonances. A reasonable estimation of the absolute line intensities for the ν₅ band of DNO₃ was performed using the ν₅ transition operator from H¹⁴NO₃. The spectrum also features the ν₅+ν₆−ν₆, ν₅+ν₇−ν₇ and ν₅+ν₉−ν₉ hot bands located at 881.03, 882.61 and 884.45 cm⁻¹, respectively.     

Line strengths of CO2: 4550-7000 cm

Line positions and strengths of ¹²C¹⁶O₂ were measured between 4550 and 7000 cm⁻¹ using near infrared absorption spectra recorded at 0.01-0.013 cm⁻¹ resolution with the McMath-Pierce Fourier transform spectrometer located at the National Solar Observatory at Kitt Peak, Arizona. These were retrieved from 42 laboratory spectra obtained at room temperature with five absorption cells having various optical path lengths (from 0.1 to 409 m) filled with natural and enriched samples of CO₂ at pressures ranging from 2 to 581 Torr. In all, band strengths and Herman-Wallis-like F-factor coefficients were determined for 58 vibration-rotation bands from the least-squares fits of over 2100 unblended line strengths; strengths of 34 of these bands had not been previously reported. Band strengths in natural abundance generally ranged from 3.30 × 10⁻²⁰ to 2.8 × 10⁻²⁵ cm⁻¹/molecule cm⁻² at 296 K. It was found that the high J transitions (J′ ? 61) of the 20012 ← 00001 band centered at 4977.8347 cm⁻¹ are perturbed, affecting both measured positions and strengths. Two other interacting bands, 21113e ← 01101e and 40002e ← 01101e, were also analyzed using degenerate perturbation theory. Comparisons with corresponding values from the literature indicate that absolute accuracies better than 1% and precisions of 0.5% were achieved for the strongest bands.     

Infrared rotation-vibration spectra of ethane: The parallel band, 2ν3, of CH3CD3

The parallel band, 2ν₃, of CH₃CD₃ is measured in the region 2715 to 2780 cm^?1 under a spectral resolution of ～0.025 cm^?1, increased to ～0.015 cm^?1 by deconvolution. About 460 lines are identified in the 2ν₃ band, and about 240 lines in a hot band arising from the first excited torsional state. Least-squares analyses with Δ₂F″ combination differences yield lower-state parameters. An individual subband analysis is undertaken because of perturbations in the vibrational bands studied. Finally, band constants are derived.