The effect of ultraviolet radiation on water vapour absorption between 5 and 50cm−1

Both field measurements and laboratory experiments suggested that absorption of UV radiation affected the near-millimetre wave absorption by water vapour. Experiments with different flux values and at different temperatures have confirmed this and pumping by UV radiation has been shown to give near-millimetre wave emission.     

Millimetre-wave and Fourier transform infrared spectra between 325 cm−1 and 4720 cm−1 of BrCN and global rovibrational analysis of the main isotopomers

The infrared absorption spectrum of BrCN has been recorded in the re?ion 325–4720 cm^?1 with a Bruker 120 HR interferometer. More than 30 000 lines have been measured and most of them have been assigned: 10734 lines for 151 bands and 10993 lines for 150 bands of ⁷⁹Br¹²C¹⁴N and ⁸¹Br¹²C¹⁴N, respectively. Also new millimetre-wave spectra were measured for the vibrational excited states lying between 1000 cm^?1 and 1400 cm-′. After a band by band analysis of these transitions, rovibrational global analyses have been performed for both isotopomers using all available experimental data. The rotational I-type resonance and the anharmonic resonance associated with k_l22 are taken into account in one-step diagonalization procedures. Sets of 73 molecular parameters are obtained for both isotopomers. It is shown that the existing equilibrium structure is likely to be reliable. The vibrational dependence of the quartic centrifugal distortion constant is analysed for the linear triatomic molecules studied so far.     

The high-resolution spectrum of water vapor between 13 200 and 16 500 cm−1

High-resolution Fourier transform spectra of water vapor between 13 200 and 16 500 cm⁻¹ have been analyzed, leading to a precise and extensive set of line positions, line intensities, and rotational energy levels of highly excited vibrational states.     

Absorption spectrum of deuterated water vapor enriched by 18O between 6000 and 9200 cm−1

The absorption spectrum of water vapor enriched by deuterium and oxygen-18 is analyzed in the 6000–9200 cm^?1 region. The spectrum has been recorded at room temperature with a Bruker IFS 120 h Fourier transform spectrometer. More than 14,000 absorption lines were measured in the recorded spectrum. The vibration–rotation assignments were performed on the basis of previously published experimental energies and of variational calculations. Nine water species (H₂¹⁶O, HD¹⁶O, D₂¹⁶O, H₂¹⁸O, HD¹⁸O, D₂¹⁸O, H₂¹⁷O, HD¹⁷O and D₂¹⁷O) were found to contribute to the observed absorption. More than 3600 lines of 19 vibrational bands of D₂¹⁸O and about 4700 lines of 16 bands of HD¹⁸O with J as high as 19 and K_a as high as 11 were assigned. The main part of the HD¹⁸O and D₂¹⁸O lines and all lines of HD¹⁷O and D₂¹⁷O were observed in the laboratory for the first time. The obtained vibration–rotation energy levels are compared with previous experimental studies and the results of variational calculations.     

The infrared spectrum of gaseous cis-d2-ethylene below 1400 cm−1

Three infrared active fundamental bands of cis-d₂-ethylene have been studied at a resolution of ca. 0.030 cm⁻¹: the type-c band ν₇ and the two type-a bands ν₆ and ν₁₂. From a simultaneous analysis of infrared ground state combination differences due to ν₇ together with microwave measurements, a set of ground state rotational and centrifugal distortion constants has been obtained. For all three bands upper state spectroscopic constants are determined, and perturbations are identified. The K′_a = 4 level in ν₇ is perturbed locally by a higher order c-Coriolis resonance with ν₈. ν₆ is globally perturbed by first-order a-Coriolis resonances with ν₄ and ν₈. For ν₁₂ a higher order c-type Coriolis resonance with 2ν₁₀ is of importance for several K_a levels, and the constants for ν₁₂ have been obtained taking this interaction into account. In addition, a Coriolis resonance parameter and some constants for 2ν₁₀ have been determined.     

CRDS of water vapor at 0.1 Torr between 6886 and 7406 cm−1

The absorption spectrum of water vapor in “natural” isotopic abundance has been recorded by high sensitivity CW-Cavity Ring Down Spectroscopy (CW-CRDS) between 6885.79 and 7405.91 cm^?1. This strong absorbing region includes the first hexad of interacting vibrational bands which was previously studied by Fourier Transform Spectroscopy. The achieved sensitivity of the recordings varies from α_min～2×10^–11 to 2×10^?10 cm^?1 allowing us to use a sample pressure of 0.1 Torr, making pressure broadening of the line profile mostly negligible. Weak lines in the vicinity of much stronger lines could then be accurately measured. The weakest lines have intensity on the order of 5×10^–28 cm/molecule at 296 K. A set of 4471 lines were assigned to 4916 transitions of five water isotopologues (H₂ ¹⁶O, H₂ ¹⁸O, H₂ ¹⁷O, HD¹⁶O and HD¹⁸O). A small number of new energy levels was determined mostly for the H₂ ¹⁷O isotopologue. The previous investigations and existing databases are critically evaluated. In particular, a number of corrections and new assignments are proposed for the water list provided by the HITRAN database in the considered region. As a result, a complete list of 12,700 transitions for water in “natural” isotopic abundance is provided as Supplementary Material for the 6885–7408 cm^?1 region.     

Thermophoresis-assisted vapour phase synthesis of CeO2 and CexY1−xO2−δ nanoparticles

Thermophoresis-assisted chemical vapour deposition (CVD) was used to produce nano-sized particles of ceria and yttria-doped ceria. The solid precursors cerium trichloride and yttrium trichloride were used with oxygen. After homogeneous nucleation, condensation and coagulation, thermophoresis-assisted particle collection was achieved in two different ways. Particle dimensions were studied by transmission electron microscopy (TEM) and X-ray diffraction (XRD)-line broadening. Crystallite and particle dimensions varied from 9 to 30 nm and from 30 to 80 nm, respectively. The influence of process conditions is discussed.     

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-sensitivity CRDS absorption spectroscopy of acetylene between 5851 and 6341 cm−1

The absorption spectrum of acetylene has been recorded at room temperature (297 K) using high-sensitivity cavity ring-down spectroscopy (α_min ～ 5×10^?11 cm^?1) in the 5851 and 6341 cm^?1 interval corresponding to a region of very weak absorption. A list of about 10,700 absorption features with estimated absolute line intensities was constructed. The smallest intensities are of the order of 5×10^?29 cm molecule^?1. The line list includes about 2500 absorption lines of ethylene present at the ppm level in the acetylene sample and identified on the basis of a high-resolution Fourier transform spectrum specifically recorded. A total of more than 2700 lines of ¹²C₂H₂ were rovibrationally assigned in comparison with accurate predictions provided by a global effective operator model. Overall, the present effort adds about 2260 new assignments to the set of about 500 assigned transitions available in the literature. The new assignments correspond to 45 new bands and 17 already-known bands, for which additional J lines were assigned. Spectroscopic parameters were derived for the upper vibrational levels from a band by band fit of the line positions (typical root mean square deviation values are of the order of 0.001 cm^?1). A few of the analysed bands were found to be affected by rovibrational perturbations, which are discussed. The new data will be valuable to refine the parameters of the global effective Hamiltonian and dipole moments of ¹²C₂H₂.     

The high-resolution infrared spectrum of HBF2: The 201 band near 1164 cm−1

The type-B totally symmetric stretching fundamental ν₂ (near 1164 cm⁻¹) of difluoroborane has been recorded. Rotational and centrifugal distortion constants have been evaluated for the two isotopic species H¹⁰BF₂ and H¹¹BF₂, in both the ground and 2¹ levels. The spectrum has been found to be regular, with no perturbations and no new information on the position of the missing fundamental ν₆.     

High resolution spectrum of Ch3OH between 8 and 100cm−1

The FIR spectrum of CH₃OH between 8–100 cm⁻¹ has been measured by a high resolution Fourier transform spectrometer. A computer best fit program, based on the Taylor series expansion of the energy levels, has been used for the line assignments. The region between 40–100 cm⁻¹ is presented for the first time. The region between 8–40 cm⁻¹, covered in a previous work, is revisited in the light of the new measurements at higher frequencies, and new assignments are given. The available microwave and radio-frequency assignments have been inserted into the fit program. A catalogue of 6725 assigned MW and FIR lines below 101.8 cm⁻¹ is presented.     

The high-resolution infrared spectrum of HBF2: The 401 band near 926 cm−1

The type-C out-of-plane bending fundamental ν₄ (near 926 cm⁻¹) in the infrared spectrum of gaseous difluoroborane, HBF₂, has been recorded at high resolution. Rotational and centrifugal distortion constants have been obtained for the two isotopic species H¹⁰BF₂ and H¹¹BF₂ in both the ground and 4¹ levels. A small rotational perturbation in the 4¹ level of H¹¹BF₂ has allowed an estimate of the position of the ν₆ fundamental, which so far has not been observed directly.     

The near infrared overtone spectrum of propyne taken by diode laser in the 12700 cm−1region

Detailed regions of the near infrared spectrum of propyne between 12737 cm-¹ and 12778cm-¹ have been measured using a simple and inexpensive home-made laser diode spectrometer. This part of the spectrum covers the overlapping 3v₁ + v₃ + v₅ and 3v₁ + v₃ + v₅ + v₁₀—v₁₀ bands. Combining a global fit and an individual profile analysis made possible the determination of the vibrational and rotational constants in each band and in some cases the resolution of the individual K structure in each transition cluster.     

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.     

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.     

The optical constants of some common low-loss polymers between 4 and 40 cm−1

The results of the determination of both the refractive index and the power absorption coefficient of seven common polymers (low and high density polyethylene, polyamide, polymethyl methacrylate, polytetrafluorethylene, polystyrene and poly 4 methyl pentene-1) at a temperature of 290K in the spectral region between 4 and 40cm⁻¹ by the techniques of dispersive Fourier transform spectrometry are presented.     

Synthesis and optical properties of La1−XCeXMnO3 studied by infrared reflectivity measurements

The bulk polycrystalline La_1−xCe_xMnO₃ (0.0 ≤ x ≤ 0.8) manganites were synthesized through citrate sol-gel auto-combustion method for a wide range of composition 0.0 ≤ x ≤ 0.8. The x-ray diffraction (XRD) analysis suggests the single phase rhombohedral (R-3c) symmetry for parent LaMnO₃ compound, however a secondary cubic (Fm-3 m) phase of cerium oxide (CeO₂) is appeared when Ce is incorporated into the LaMnO₃. A detailed XRD study of these materials were discussed, and specifically the infrared reflectivity measurements on La_1−xCe_xMnO₃ materials are discussed in this study for the first time. The phonon softening and hardening was observed for different modes but softening was found to be more pronounced which implied strong electron–phonon coupling. The most affected phonon mode was appeared for the doping range 0.2 ≤ x ≤ 0.4, in which the largest softening was observed. The Lyddane–Sachs–Teller relation is verified by experimental FTIR data.     

The absorption spectrum of 12C2H2 between 12800 and 18500cm−1 II. Rotational analysis

The rotational structure of the vibrational bands of ¹²C₂H₂ is investigated in three spectral energy regions not previously systematically explored at high resolution, 12800–13500 cm^?1, 14000–15200 cm^?1 and 16500–18360 cm^?1, on the basis of new spectral data recorded by intracavity laser absorption spectroscopy. The rotational analysis of 17 new absorption bands arising from the ground state is reported (11 Σ_u ⁺ ? Σ_g ⁺ bands and 6Π_u ? Σ_g ⁺ bands). Four bands in the range studied show strong perturbations affecting both the line positions and intensities. Their detailed analysis is performed in order to determine the nature of the coupling schemes, the vibrational species and the rotational constants of the perturber states. Altogether, the vibration-rotation parameters of 21 newly observed vibrational states are derived.     

The Emission Spectrum of Hot Water in the Region between 370 and 930 cm−1

An emission spectrum of the water molecule at a temperature of 1550°C has been recorded in the range from 373 to 933 cm⁻¹. More than 4000 pure rotational lines were observed with the strongest belonging to the ground state (000) and the first excited bending vibrational level (010). Transitions involving rotational quantum numbersJandK_asignificantly higher than previously recorded have been assigned.     

Laser infrared spectroscopy of vinyl fluoride in the 1280–1400 cm−1 region

The infrared spectra of CH₂=CHF have been investigated in the ν₅ and ν₆ band regions between 1280 and 1400?cm^?1, at a resolution of about 0.002?cm^?1, using a tunable diode laser spectrometer. These vibrations of symmetry species A′ give rise to a/b-hybrid bands with different contributions from both the components. Spectral analysis resulted in the identification of 1565 (J≤46, K _a ≤11) and 1651 (J≤48, K _a ≤15) transitions of the ν₅ and ν₆ fundamentals, respectively. Both bands are perturbed by the nearby states ν₈?+?ν₉ and ν₉?+?ν₁₁ through different Coriolis resonances and an anharmonic interaction. Using Watson's A-reduction Hamiltonian in the I^r representation and perturbation operators almost all the transitions have been fitted simultaneously to a model including six resonances within the tetrad ν₅/ν₆/ν₈?+?ν₉/ν₉?+?ν₁₁. A set of spectroscopic constants for the ν₅ and ν₆ bands, as well as parameters for the dark states ν₈?+?ν₉ and ν₉?+?ν₁₁ and coupling constants, have been determined. From spectral simulations the dipole moment ratio |Δμ _a /Δμ _b | was estimated to be 0.6?±?0.1 and 2.0±0.3 for the ν₅ and ν₆ bands, respectively.