Line intensities of CO2 in the 2·7 micron region

Individual line intensities have been measured at 0·025 cm^?1 resolution and low pressures for the two strong Σ-Σ bands of C¹²O₂¹⁶ near 2.7 microns, as well as for their associated Π-Π hot-bands. Values of the rotationless dipole-moment matrix elements and vibration-rotation interaction coefficients are reported along with total band intensities. Results for the latter in cm^?2 atm^?1 at 296°K are: 25·7, 1·96, 39·3 and 3·23 for the 02⁰1-00⁰0, 03¹1-01¹0, 10⁰1-00⁰0, and 11¹1-01¹0 bands, respectively.     

Heterodyne frequency measurements on N2O between 1257 and 1340 cm−1

Frequency measurements are given for the 00⁰1-00⁰0 and 01¹1-01¹0 bands of N₂O from 1257 to 1340 cm^?1. The measurements utilize heterodyne techniques by measuring small frequency differences between a tunable diode laser locked to the center of an N₂O absorption line and harmonic combinations of frequencies of radiation from two CO₂ Lamb-dip-stabilized lasers. The measurements are facilitated by the use of the CO laser as a transfer laser whose frequency is also measured. These measurements have been combined with other data to provide new band constants and frequency calibration tables for several band systems of N₂O in the following regions; 1215 to 1340, 1816 to 1930, and 2135 to 2268 cm^?1. A correction factor is also provided for existing calibration tables near 590 cm^?1.     

Laser Stark spectroscopy of FCN

Using a CO₂ laser, Stark shifted resonances have been measured for the CF stretching fundamental (ν₃) of FCN near 9.3 μm, and for two nearby “hot” bands. The band centers measured are 1076.492007 ± 0.000013 cm^?1 for 00⁰1-00⁰0, 1085.741046 ± 0.000050 cm^?1 for 01¹1-01¹0, and 1091.16222 ± 0.00015 cm^?1 for 02⁰1-02⁰0. The ground state dipole moment of FCN is found to be 2.1203 ± 0.0010 D and dipole moments are also given for the other states observed. Values are given for the rotational constant and l-doubling constant for the 01¹1 state.     

High-resolution infrared spectrum of the 859- and 1711-cm−1 bands of carbonyl sulfide (OCS)

The ν₁ and 2ν₁ bands of OCS have been measured using grating spectrometers and a tunable diode laser spectrometer. Preliminary wavenumbers for OCS absorption lines useful for calibrating tunable laser systems are given for the wavenumber intervals 825 to 885 cm^?1 and 1665 to 1737 cm^?1. Measurements and an analysis are given for the bands 10⁰0-00⁰0, 11¹0-01¹0, 20⁰0-00⁰0, 21¹0-01¹0, and 30⁰0-10⁰0 of the ¹⁶O¹²C³²S isotopic species and for the 20⁰0-00⁰0 band of the ¹⁶O¹³C³²S and ¹⁶O¹²C³⁴S species. Effective band constants are given for these bands.     

Line strengths and self-broadened linewidths of N2O in the 2-μm region: 2400-0000 and 0112-0000 transitions

The strenghths and self-broadened linewidths of the parallel 24⁰0-00⁰0 and perpendicular 01¹2-00⁰0 bands of N₂O have been measured with a precision better than 3%, using a deconvolution procedure. For both transitions, the coefficient of the vibration-rotation interaction polynomial, the values of the rotationless dipolar transition moment, and the band intensity have been calculated from the line strengths. For the total intensity the values found are S_00⁰0²⁴⁰⁰ = (1.325 ± 0.021) × 10^?2 cm^?2·atm^?1 and S_00⁰0⁰¹¹² = (1.209 ± 0.018) × 10^?2 cm^?2·atm^?1.     

Infrared spectrum of HCN and HCN

The high-resolution spectrum of H¹²C¹⁴N has been measured near 4870 and 6060 cm⁻¹. The following bands have been identified and analyzed: 01¹2-00⁰0, 02⁰2-01¹0, 02²2-01¹0, 04⁰1-00⁰0, 11¹1-00⁰0, 12⁰1-01¹0, and 12²1-01¹0. The C---N stretching fundamental (ν₃) of H¹²C¹⁵N has also been measured near 2100 cm⁻¹. This fundamental is found to be 3 cm⁻¹ higher than previously reported. Other bands that have been identified in the H¹²C¹⁶N spectrum are 03¹0-00⁰0, 04⁰0-01¹0, 04²0-01¹0, and 01¹1-01¹0.     

Laser Stark spectroscopy of DCN and DC15N

Using a CO laser, laser Stark resonance spectra were measured for the CN stretching fundamentals (the 00⁰1-00⁰0 bands) of D¹²C¹⁴N and D¹²C¹⁵N near 1925 cm^?1. Laser Stark resonances were also measured for the hot band 01¹1-01¹0 of D¹²C¹⁴N. In addition to accurately determining the band centers, dipole moments are given for the different vibrational states involved.     

Analysis of the Fourier transform spectrum of 13C18O2 in the 4.3- and 16-μm regions

Fourier transform spectra have been obtained for ¹³C¹⁸O₂ in the regions of ν₂ (16 μm) and ν₃ (4.3 μm) at a resolution of 0.04 cm^?1. From a least-squares fit of the P- and R-branch lines for the transitions, values have been calculated for the rotational constants B, the centrifugal distortion constants D, and the band origins. Based on the derived constants, the calculated wavenumbers for the P and R lines of both the 01¹0-00⁰0 and 00⁰1-00⁰0 transitions agree with the observed positions within ±0.003 cm^?1. We have also observed the difference bands ν₁-ν₂ and the hot bands (ν₃ + ν₂) ? ν₂. From an analysis of these transitions we have determined values for the l-doubling constants for ν₂ and the location of the inactive fundamental ν₁.     

High resolution infrared spectrum of 13CS2 between 250 and 430 cm−1

The high resolution infrared spectrum of ¹³CS₂ between 250 and 430 cm^?1 has been studied with a Fourier transform spectrometer at a resolution of about 0.010 cm^?1. The following bands are analyzed: the bending fundamental 01¹0←00⁰0 of ¹³C³²S₂ and the associated “hot” bands 02²0←01¹0, 02⁰0←01¹0, 03³0←02²0, 03¹0←02⁰0, 03¹0←02²0, 11¹0←10⁰0, the difference band 10⁰0←01¹0 of ¹³C³²S₂, and the bending fundamental 01¹0←00⁰0 of ³²S¹³C³⁴S. The polynomial fits were used in the analyses. The rotational constants B and D together with the vibrational term values have been derived for the states involved. The l-type doubling constant q has been obtained for the Π-states 01¹0, 11¹0, and 03¹0 of ¹³C³²S₂.     

High resolution infrared spectra of isotopic carbon disulfide: The 2ν1 + ν3 band

The 20⁰1-00⁰0 bands of ¹²C³⁴S₂ and ¹³C³⁴S₂ have been measured with a resolution of 0.03 cm^?1. The following “hot” bands associated with this transition were also measured and analyzed: 21¹1?01¹0, 30⁰1–10⁰0 for both the isotopic forms. For ¹²C³⁴S₂, we have also recorded the Δ-Δ transition 22²1–02²0. In addition, the 20⁰1-00⁰0 bands of the isotopic species ¹²C³²S³⁴S were measured.     

Measurement at different temperatures of absolute intensities,line half-widths,and broadening by Ar and N2 for the 3001II←0000 band of CO2

Absolute intensities, self-broadening coefficients, and foreign-gas broadening by Ar and N₂ were measured at temperatures of 197, 233 and 294 K for the 30⁰1_II←00⁰0 band of CO₂ at 6348 cm^-1. Also, the intensity parameters and total band intensity were calculated. We obtained for the vibration-rotation interaction factor the value F(m) = 1 + (0.26 ± 0.06) × 10^-2m + (0.92 ±0.32 × 10^-4 m²; for the purely vibrational transition moment, we found ¦R₀₀₀₀^3001_II¦к(0.4351 ± 0.0014)()10^b3 debye; and, for the total band intensity at STP conditions, S_band(30⁰1_II←00⁰0)_STP = 1255 ± 9 cm^-1 km^-1 atm^-1.Self-broadening coefficients at 197 and 294 K were also measured, as well as broadening by Ar and N₂. Foreign-gas-broadening efficiencies (Ar and N₂) were determined. Finally, a comparison is made with measurements by other authors and with theoretically calculated values.     

Vibration-rotation bands of isotopic carbon disulfide at 4.6 μm

The 10⁰1-00⁰0 bands of ¹²C³⁴S₂ and ¹³C³⁴S₂ have been measured with a resolution of 0.03 cm^?1. The following “hot” bands associated with this transition were also measured and analyzed: 11¹1-01¹0, 20⁰1–10⁰0 for both isotopic forms. For ¹²C³⁴S₂, the Δ-Δ transition 12²1–02²0 has also been observed. In addition, the 10⁰1-00⁰0 bands of the isotopic species ¹²C³²S³⁴S and ¹²C³³S³⁴S were measured.     

Infrared spectra of CS2: Measurement of “hot” bands associated with the 2325 cm−1 and 2962 cm−1 bands

The 12⁰1-00⁰0 and 02⁰1-00⁰0 transitions of CS₂ have been measured with a resolution of 0.025 cm^?1. The following “hot” bands associated with these transitions were also measured 13¹1?01¹0, 22⁰1? 10⁰0, 14⁰1?02⁰0, 14²1?02²0, 03¹1?01¹0, 12⁰1?10⁰0, 04⁰1?02⁰0, 04²1?02²0, 13¹1?11¹0, and 22⁰1?20⁰0. Improved rotational constants are given for the ground state and the first bending state. A consistent set of band constants is given for all the above vibrational transitions.     

Time-dependent self-consistent perturbation theory and applications to molecules

The two most intense bands of the 370 nm electronic band system of tropolone have been rotationally analysed. They are separated by 18·93 cm^-1 and it has been shown that the high wavenumber band is the 0^--0^- (H₁ ¹) transition in what is almost certainly the internal hydrogen-bonding vibration v _H : the low wavenumber band is the 0⁺-0⁺ (0₀ ⁰) transition. A rotational contour analysis of both bands shows that there is an intensity alternation in K _a″ such that the ratio K _a″ even : odd is 10 : 6 in the 0⁺-0⁺ band and 6 : 10 in the 0^--0^- band. The intensity alternation, the nearly equal intensities of the 0⁺-0⁺ and 0^--0^- bands, the separation of these two bands and the anharmonic behaviour of v _H show that the separation of the 0⁺ and 0^- levels is small in the ground electronic state (probably less than 50 cm^-1) and is 18·93 cm^-1 larger in the excited electronic state.

The 0⁺-0⁺ and 0^--0^- bands are both type B showing that the electronic transition is à ¹ B ₂-X ¹ A ₁ and therefore π*-π rather than π*-n. The π*-n transition is probably shifted to high wavenumber by the internal hydrogen-bonding.     

New infrared integrated band intensities for HC3N and extensive line list for the ν5 and ν6 bending modes

The infrared spectrum of cyanoacetylene (also called propynenitrile) has been investigated from 400 to 4000 cm⁻¹ at a resolution of 0.5 cm⁻¹. Integrated intensities of the main bands and a number of weaker bands have been obtained with an uncertainty better than 5%. Inaccurate values in previous studies have been identified in particular concerning the intensity of the strong ν₅ stretching band at 663.2 cm⁻¹. Former results on the temperature dependence of integrated intensities have also been revisited.Synthetic spectra calculation has been performed for the ν₅ and ν₆ bands on the basis of the best available high resolution data. It has been shown that the GEISA line parameters for HC₃N are not sufficient to reproduce the band intensities and some hot band features observed in our experimental spectra at room temperature. As a first step, the model spectra has been improved by including a number of missing hot subbands and by calculating accurately the hot band relative intensities. Finally, a perfect agreement between calculated and observed spectra was achieved on the basis of a global analysis of HC₃N levels up to 2000 cm⁻¹ combined with the new integrated intensity measurements. A new extensive line list for the ν₅ and ν₆ bending modes of HC₃N has been compiled.     

Sequence and Hot Transitions in the Co2 Molecule; Interference of Adjacent Lines Belonging to Different Transitions as a Function of Temperature

Carbon-dioxide spectra of some higher transitions in the 9-11μm region were studied. Spectra of the sequence ([10°1,02°1]_I,II - 00°2) and hot (01¹1 - 11¹0) bands were calculated as a function of temperature. the positions of the ro-vibrational transitions and their intensities were determined as a function of temperature. for lines in hot and sequence transitions whose positions are close to some of the regular lines ([l0⁰0,02⁰0]_I,II - 00°1)¹ absorption coefficients of adjacent lines were calculated as functions of line center distances and temperature. the resulting values of the absorption coefficient for conditions of constant pressure or constant volume were determined.     

N2- and O2-broadening of CO2 for the (301)III ← (000) band at 6231 cm

The N₂- and O₂-broadening effect have been investigated for 10 absorption lines of the CO₂ (30⁰1)_III ← (00⁰0) band centered at 6231 cm⁻¹, in the range from P(28) to R(28) by a near-infrared diode-laser spectrometer. We have analyzed the observed line profiles with the Galatry function, and determined the N₂- and O₂-broadening coefficients precisely. The air-broadening coefficients for these lines have been derived. The present results are compared with those of the previous studies for this band and with some of the other bands.     

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.     

A study of the fundamental and first overtone bands of NO in NO-rare gas mixtures at pressures up to 10,000 PSI

The absorption intensities of the 1-0 and 2-0 vibration-rotation bands of NO are determined from the absorption coefficients of NOHe and NOAr gaseous mixtures at high pressures at room temperature. The values obtained are: A_1-0 = 121 ± 6 cm^?2 Agt^?1 and A_2-0 = 2.17 ± 0.11 cm^?2 Agt^?1. A theory developed by Tipping is applied to evaluate the dipole moment coefficients unambiguously, including their signs, from the absolute intensity values and the difference between the mean frequency factor and the band origin. The following expansion for the dipole moment function in the ground state of NO is determined: M(x) = ?0.166 + 2.54x ? 1.99x² (in Debye). The absorption profiles of both the 1-0 and 2-0 bands in NOAr mixtures show marked changes as gas pressure increases; some of the factors influencing the shapes of the bands are also discussed. The plots of the integrated intensity vs rare gas density are found to be straight lines with positive slopes. This linear increase of the band intensity with density is interpreted as mainly due to the apparent induced absorption.     

Remeasurement of the absolute intensities of CFC11 (CFCl3) and CFC12 (CF2Cl2)

The absolute intensities of the strong absorption bands of CFC11 (CFCl₃) and CFC12 (CF₂Cl₂) have been remeasured at 300 K in view of their importance in global climatic impact and ozone depletion studies. For CFC11, our new values are 1718 ± 17 cm⁻² atm⁻¹ (846 cm⁻¹ band) and 671 ± 8 cm⁻² atm⁻¹ (1085 cm⁻¹ band). The values we have now obtained for the CFC12 intensities are 1421 ± 12 cm⁻² atm⁻¹ (923 cm⁻¹ band), 1129 ± 11 cm⁻² atm⁻¹ (1102 cm⁻¹ band), and 717 ± 14 cm⁻² atm⁻¹ (1161 cm⁻¹ band).