The absorption spectrum of 12C2D2 in the 10000–12500 cm−1 spectral region

The absorption spectrum of dideuteroacetylene has been recorded by intracavity laser absorption spectroscopy (ICLAS) in the 10 200–12 500cm^?1 spectral region. Among 25 absorption bands of ¹²C₂D₂ rotationally analysed in this spectral region, 17 are newly observed. They include one II_u-Σ⁺ _g and thirteen Σ⁺ _u-Σ⁺ _g bands starting from the vibrational ground state and eleven hot bands from the V ₄ = 1 and V ₅ = 1 lower states. The rotational structure of two excited levels is affected by a strongly J-dependent interaction with a perturber which induces intensity transfer to extra lines. The coupling is identified as a I-resonance interaction with δ_u dark states and the vibrational assignment of the perturbers is discussed. Two Σ-Σ bands of the ¹²C¹³ CD₂ species, present in natural abundance in the sample, could also be identified and rotationally analysed. Most of the corresponding excited vibrational levels of ¹²C₂D₂ were unambiguously assigned using the polyad model [Herman, M., el idrissi, M. I., Pisarchik, A., Campargue, A., Gaillot, A.-C., Biennier, L., di lonardo, G. and Fusina, L., 1998, J. chem. Phys., 108, 1377] which allows vibrational energies and B _V rotational constants to be predicted. In particular the previously highlighted 1/244 anharmonic resonance is confirmed by energy and intensity features in several {(V ₁, V ₂, V ₃, V ₄ = 0, V ₅ = 0),(V ₁ ?1, V ₂ + 1, V ₃ V ₄ = 2, V ₅ = 0)} dyads. Significant deviations between predicted and experimental energy levels are observed for a few levels and discussed.     

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.     

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.     

The high-resolution infrared spectrum of ethylene in the 1800–2350 cm−1 spectral region

Fourier transform spectra of ethylene (C₂H₄) have been recorded in the 1800–2350?cm^?1 (4.3–5.6?µm) spectral region using a Bruker IFS125HR spectrometer at a resolution of 0.004?cm^?1 leading to the observation of six vibrational bands, ν ₇?+?ν ₈, ν ₄?+?ν ₈, ν ₆?+?ν ₁₀, ν ₆?+?ν ₇, ν ₄?+?ν ₆ and ν ₃?+?ν ₁₀. The corresponding upper state ro-vibrational levels were fit using a Hamiltonian matrix accounting for numerous interactions. A satisfactory fit could be obtained using a polyad of nine interacting states {8¹10¹,?7¹8¹,?4¹8¹,?8¹12¹,?6¹10¹,?6¹7¹,?4¹6¹,?3¹10¹,?3¹7¹} of which three (8¹10¹, 8¹12¹ and 3¹7¹) are unobserved dark states. As a result a much more accurate and extended set of Hamiltonian constants were obtained than previously derived. The following band centers were determined: ν ₀(ν ₇?+?ν ₈)?=?1888.9783(20)?cm^?1, ν ₀(ν ₄?+?ν ₈)?=?1958.2850(20)?cm^?1, ν ₀(ν ₆?+?ν ₁₀)?=?2047.7589(20)?cm^?1, ν ₀(ν ₆?+?ν ₇)?=?2178.011(60)?cm^?1, ν ₀(ν ₄?+?ν ₆)?=?2252.8026(24)?cm^?1 and ν ₀(ν ₃?+?ν ₁₀)?=?2171.2397(20)?cm^?1. Finally, a synthetic spectrum that could be useful for ethylene detection in planetary atmospheres was generated.     

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.     

The infrared spectrum of 12C2HD: the stretching–bending combination bands in the 1800–4700 cm−1 region

The infrared spectrum of ¹²C₂HD has been observed between 1800 and 4700?cm^?1 by Fourier transform spectroscopy. The ν₁, ν₂ and ν₃ absorption bands and the associated hot and combination bands involving the bending modes up to υ_t?=?υ₄?+?υ₅?=?2 have been investigated. Altogether, 60 vibrational bands were analysed, leading to the spectroscopic characterization of 31 vibrationally excited states. Several perturbations have been observed, but the transitions involving the perturbing states have not been detected. As a consequence, an appropriate treatment of the vibrational or ro-vibrational interactions has not been possible. A tentative assignment of the perturbing states has been proposed. Eventually, global fits for each fundamental vibration and its associated cold and hot bands have been performed.     

The Assignment of the 1600 cm−1 Mystery Band of Carbons

Abstract

The assignment of a band near 1600 cm^?1 in IR spectra of carbons has been controversial for four decades. However, many different carbons have been studied: effectively, a single band assignment was sought for an absorption appearing with three different classes of carbon. As these differ in over-all structure, not one but three explanations are needed. These are discussed. However, undue emphasis has been placed on a single absorption; attention should also be paid to other absorptions accompanying the 1600 cm^?1 band.     

LED-based Fourier-transform spectroscopy of H2 18O in the range 15000–15700 cm−1

The spectrum of H₂ ¹⁸O in the range 15000–15700 cm^?1 has been recorded for the first time on a Fourier-transform spectrometer using a high-brightness light-emitting diode as a radiation source. The measurements have been conducted at room temperature with a resolution of 0.05 cm^?1. A threshold sensitivity in absorption of 2 × 10^?7 cm^?1 has been achieved due to both the use of a light-emitting diode and optimization of the multipass cell with a base length of 60 cm, which ensured a 19.2-m length of the absorbing layer. A high signal-to-noise ratio (S/N = 2000–10000) made it possible to record about 670 water-vapor lines with intensities of 1.0 × 10^?26–2.2 × 10^–24 cm/mol at 296 K. The energies of 265 vibrational-rotational levels of the H₂ ¹⁸O molecule are determined and attributed to seven vibrational states, namely, (033), (113), (212), (231), (311), (330), and (410).     

Heterodyne frequency measurements on N2O near 1060 cm−1

The results of heterodyne frequency measurements are given for the 10⁰0-02⁰0 band of N₂O centered at 1056 cm⁻¹. Nine lines are measured and fit with an rms deviation of 1.3 MHz. The data are combined with other infrared and microwave data in a least-squares fit that gives accurate ro-vibrational constants for the two states involved in these transitions. The analysis of the data is based on a treatment that includes the effect of l-type resonance between the 02⁰0 and 02²0 states. Derived tables of wavenumbers are given for the 02⁰0-00⁰0 band near 1168 cm⁻¹ and the 02⁰1-00⁰0 band near 2460 cm⁻¹.     

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.     

Spectral Study of Some Samarium Complexes in the Region 750–250 cm−1

Abstract

Rare earth β -diketonates and diketo-ester complexes are promising laser materials due to narrow line width of the internal 4fⁿ transitions and weak crystal-field interactions¹. The electronic energy states², spectral intensities^3–5, bonding^6,7 and infrared spectra^8–11 of some of these complexes have been recently reported by the authors. However, little information regarding their structure and strengths of various bonds are available. The infrared spectra of rare earth complexes in the spectral region 4000 – 750 cm^?1 are characteristic of the ligand, while those in the region 750 – 250 cm^?1 characterize the metal-ligand bonding. The present communication reports the values of force constants computed from the observed infrared absorption spectra of four ethyl 1-methyl acetoacetate (EMA) and ethylbenzoylacetate (EBA) complexes of trivalent samarium in the region 750 – 250 cm^?1.     

The absorption spectrum of H2 18O in the range 13400–14460 cm?1

Using a Fourier-transform spectrometer, we have measured the absorption spectrum of H₂ ¹⁸O vapor in the range 13400?C14460 cm^?1 at room temperature with a resolution of 0.03 cm^?1 and a threshold sensitivity in absorption of 10^?6 cm^?1. With a multipass cell, the volume of which was 3 L and the base of which was 25 cm, a length of the absorbing layer of 10 m has been achieved. A high signal-to-noise ratio, on the order of 1000, has allowed us to detect about 700 lines of the H₂ ¹⁸O molecule, the intensities of which were as low as 10^?25 cm/molecule, at 296 K. The observed lines have been attributed to eleven vibrational-rotational bands of the molecule.     

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.     

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.