Fourier transform spectra of the 3300 cm−1 bands of HCN

The 3300-cm⁻¹ bands of various isotopes of HCN have been measured with a resolution of about 0.01 cm⁻¹ using the Fourier transform spectrometer constructed by J. Brault and co-workers at the National Solar Observatory. The frequencies of 910 HCN lines obtained from absorption spectra of three different isotopic species are reported with an accuracy of approximately 0.0001 cm⁻¹. Six bands of HCN, four bands of H¹³CN, and two bands of HC¹⁵N were analyzed to obtain band origins, rotational constants, and l-doubling constants. The first (11¹0 ← 01¹0) and second (12⁰0 ← 02⁰0 and 12²0 ← 02²0) hot bands of H¹³CN are measured at high resolution for the first time. The fine structures of the Q branches of (110 ← 010), (12²0 ← 02²0), and (13³0 ← 03³0) “hot bands” of HCN have been completely resolved and measured. The accuracies of the calculated band origins are better than 0.0001 cm⁻¹ for most bands, and the upper state rotational constants (B′) have accuracies which range from 1 × 10⁻⁷ to 5 × 10⁻⁶ cm⁻¹ (0.003 to 0.015 MHz).     

Fourier transform spectra of the 2100-cm−1 bands of HCN

The 2100-cm⁻¹ bands of various isotopes of HCN have been measured with a resolution of about 0.01 cm⁻¹ using the Fourier transform spectrometer constructed by J. Brault and co-workers at the National Solar Observatory. The frequencies of 500 HCN lines obtained from absorption spectra of three different isotopic species are reported with an accuracy of approximately 0.0001 cm⁻¹. Six bands of HCN, two bands of H¹³CN, and two bands of HC¹⁵N were measured. The 001 ← 000 and 03¹0 ← 000 of H¹³CN were reported for the first time. New measurements of 03³0 ← 000 forbidden transitions (Δl = 3) were made.     

Fourier transform spectroscopy of methanol: Taylor coefficients for the region between 8 and 80 cm−1

In our systematic investigation of the FTS of CH₃OH we have assigned about 3000 lines connecting levels of the vibrational ground state with frequencies between 8 and 80 cm⁻¹. Here we present the parameters for Taylor expansions of the energy levels in J(J + 1) which allow us to reconstruct the spectral lines with a precision usually of the order of 10⁻⁴cm⁻¹.     

HSSH revisited: The high-resolution Fourier transform spectrum of the ground state between 30 and 90 cm−1

The spectrum of disulfane (HSSH) between 30 and 380 cm⁻¹ has been recorded in absorption using a new high-resolution Fourier transform spectrometer at the Justus-Liebig Universität Giessen. The spectrometer is briefly described, as well as procedures concerning the synthesis and handling of this quasi-stable species. A combined analysis of previous microwave data on the HSSH ground state and over 600 newly assigned lines between 30 and 90 cm⁻¹ has been carried out, yielding the effective spectroscopic parameters of the Watson S-reduced Hamiltonian. Examples of the strikingly simple perpendicular spectrum of this nearly symmetric prolate rotor are presented.     

Stimulated emission of atmospheric water vapour between 2 cm−1 and 30 cm−1 photoinduced by infrared radiation

Fourier spectra of humid air in a 0.8 m path when it was illuminated by a combined flux of millimetre waves, infrared and ultraviolet showed millimetre wave maser action pumped by the infrared component.     

Fourier spectrum of CH3OH between 950 and 1100 cm−1

The infrared spectrum ofCH₃OH between 950 and HOOcm⁻¹ has been measured by a high resolution Fourier transform spectrometer. This spectral region is of particular interest because of its overlapping with the CO₂ laser emissions used for exciting the CH₃OH laser. A catalog of 3410 assigned lines is presented, as well as the Taylor development tables for evaluating the energies of the upper levels of the corresponding transitions.     

High-resolution infrared Fourier transform spectroscopy of SO in the X3Σ− and a1Δ electronic states

The v = 1 ← 0 vibration-rotation absorption bands of ³²S¹⁶O, ³⁴S¹⁶O, and ³²S¹⁸O in the ground electronic state, X³Σ⁻, and the v = 1 ← 0 vibration-rotation band of ³²S¹⁶O in the first excited electronic state, a¹Δ, were measured at 0.004 cm⁻¹ unapodized resolution with a high-resolution Fourier transform spectrometer coupled to a long path absorption cell. The v = 2 ← 0 vibration-rotation band of ³²S¹⁶O in the X³Σ⁻ state was also observed. Line positions for P- and R-branch transitions up to N = 44 for ³²S¹⁶O have been measured and analyzed yielding improved molecular parameters. The present measurements are compared with previous infrared and microwave measurements.     

Fourier transform infrared spectrum of carbon disulphide in the 4ν2 + ν3 band region near 3100 cm−1

Fourier transform spectra have been recorded for carbon disulphide CS₂ in the region of the 4ν₂ + ν₃ band near 3100 cm^?1. The data analysis has determined new molecular constants. Bands were also observed for the isotopomer ¹²C³²S³⁴S.     

Spectra of carbon disulphide in the 3400–4400 cm−1 region by Fourier transform spectroscopy

Fourier transform spectra have been recorded for carbon disulphide (CS₂) in the region between 3400 cm^?1 and 4400 cm^?1. A data analysis has determined new molecular constants: 14 bands were observed for the main isotopic form ¹²C³²S₂, two bands for the isotopomer ¹²C³²S³⁴S and one each for ¹²C³²S³³S and ¹³C³²S₂.     

Detection and analysis of four new bands in CRDS 16O3 spectra between 7300 and 7600 cm−1

The absorption spectrum of the ¹⁶O₃ isotopologue of ozone was recorded in the 7000–7920 cm^?1 region by using high sensitivity CW-Cavity Ring Down Spectroscopy (α_min ～ 10^?10 cm^?1). This report is devoted to the analysis of the 7300–7600 cm^?1 region dominated by four A-type bands: 6ν₁ + ν₃ centred around 7395 cm^?1, 3ν₁ + 5ν₂ + ν₃ and 2ν₁ + 4ν₂ + 3ν₃ lying in the 7450 cm^?1 region and 5ν₁ + 2ν₂ + ν₃ centred around 7579 cm^?1. 213 transitions of the 6ν₁ + ν₃ band were assigned and the corresponding line positions were modeled using an effective Hamiltonian including a Coriolis resonance interaction between the (601) upper state and a A-type dark state. The two very close 3ν₁ + 5ν₂ + ν₃ and 2ν₁ + 4ν₂ + 3ν₃ bands were analysed using a similar effective Hamiltonian scheme involving the anharmonic resonance coupling between the (351) and (243) states. For these two bands, 304 transitions were assigned. The modelling also includes a first Coriolis resonance interaction between the (351) bright state and the (530) dark state, and a second one between the (243) bright state and the (144) dark state. In the 7579 cm^?1 region, 205 transitions of the 5ν₁ + 2ν₂ + ν₃ band were assigned and modelled taking into account the Coriolis resonance interactions between the (521) upper state and the (700), (342) and (280) dark states.The dipole transition moment parameters of the four analysed bands were determined by a least-squares fit to the measured line intensities. For the studied band systems, the effective Hamiltonian and transition moment operator parameters were used to generate line lists provided as Supplementary Materials.     

Retrieval algorithm of quantitative analysis of passive Fourier transform infrared （FTRD） remote sensing measurements of chemical gas cloud from measuring the transmissivity by passive remote Fourier transform infrared

Passive Fourier transform infrared （FTIR） remote sensing measurement of chemical gas cloud is a vital technology. It takes an important part in many fields for the detection of released gases. The principle of concentration measurement is based on the Beer-Lambert law. Unlike the active measurement, for the passive remote sensing, in most cases, the difference between the temperature of the gas cloud and the brightness temperature of the background is usually a few kelvins. The gas cloud emission is almost equal to the background emission, thereby the emission of the gas cloud cannot be ignored. The concentration retrieval algorithm is quite different from the active measurement. In this paper, the concentration retrieval algorithm for the passive FTIR remote measurement of gas cloud is presented in detail, which involves radiative transfer model, radiometric calibration, absorption coefficient calculation, et al. The background spectrum has a broad feature, which is a slowly varying function of frequency. In this paper, the background spectrum is fitted with a polynomial by using the Levenberg-Marquardt method which is a kind of nonlinear least squares fitting algorithm. No background spectra are required. Thus, this method allows mobile, real-time and fast measurements of gas clouds.     

The determination of complex refractive index spectra of liquids in the far-infrared spectral region 5–500cm−1, with dispersive Fourier transform spectrometry

The complex refractive index spectrum of transparent as well as very absorbing liquids is determined in the far-i.r. spectral region 5–500cm⁻¹ from dispersive interferograms obtained with a variable thickness, variable temperature cell containing the liquid specimen confined between a displaceable mirror and a plane-parallel window. The complex refractive index spectrum of the window material (e.g. hyperpure silicon, crystal quartz) is determined with the same experimental setup from an empty-cell interferogram.     

Analysis of infrared thermoreflectance spectra of NbxTi1−xS2

Thermoreflectance spectra of Nb_xTi_1−xS₂ crystals in the infrared are reported and discussed. In particular the plasmon lineshape, an interband transition at ≅0.8 eV and the effect of cation substitution on infrared thermoreflectance spectra are examined.     

Fourier transform measurements of H218O and HD18O in the spectral range 1000–2300 cm−1

The spectra of water vapor enriched by ¹⁸O were recorded in the 1000–2300 cm^?1 spectral range, which corresponds to the spectral region studied by IASI instrument (Infrared Atmospheric Sounding Spectrometer) instrument. The spectra were recorded by a step by step Fourier Transform Spectrometer (FTS) at room temperature with absorption path lengths up to 36 m. Positions, intensities and self broadening coefficients of about 1800 lines of H₂¹⁸O and 900 of HD¹⁸O were analyzed and all the transitions were assigned. This paper focuses on lines intensities and comparisons with data from literature are presented. An average difference of 10% with HITRAN2008 database H₂¹⁸O line intensities is found with a maximum discrepancy of about 25% for the ν₁–ν₂ band.