The v 1 and v 3 bands of ND3

High resolution (0.004cm^-1 instrumental bandwidth) interferometric Fourier transform infrared spectra of ¹⁴ND₃ were obtained on a BOMEM DA002 spectrometer under essentially Doppler limited conditions. An analysis is reported of the ND₃ stretching fundamentals with band centres at [EQUATION]₁ ⁰ (s ← a) = (2420.056 ± 0.001)cm^?1, [EQUATION]₁ ⁰(a ← s) = (2420.650 ± 0.001)cm^?1, [EQUATION]₃ ⁰(a ← a) = (2563.8840 ± 0:0005)cm^?1 and [EQUATION]₃ ⁰ (s ← s) = (2563.9161 ± 0.0005)cm^?1, with inversion tunnelling splittings Δ[EQUATION]₁ = 0.5412cm^?1 and Δ[EQUATION]₃ = 0.0209cm^?1 in the vibrationally excited levels. About 50 parameters of the effective Hamiltonian for this band system could be determined accurately. Assignments were established with certainty by means of ground state combination differences. The results are important for and are discussed in relation to the mode selective inhibition and promotion of inversion at the nitrogen atom by exciting ND stretching vibrations, and treatments of isotope e? ects on inversion of ammonia by means of effective Hamiltonians and true molecular Hamiltonians on high dimensional potential hypersurfaces.     

High resolution FTIR spectra and analysis of the ν11 fundamental and of the ν2 + ν11, ν5 + ν12 and ν7 + ν16 combination bands of 12C6D6

We report results from measurements of the high resolution FTIR spectrum for the fully deuterated benzene molecule C₆D₆ in the range 450–3500 cm^?1. Accurate spectroscopic constants have been obtained for the fundamental vibration ν₁₁ at 496.208 cm^?1 and improved ground state constants have been deduced from a fit of ground state combination differences. The J structure of the combination parallel bands ν₂ + ν₁₁ (at 2798.1 cm^?1), ν₅ + ν₁₂ (1802.5 cm_?1) and ν₇, + ν₁₆ (2619.3 cm^?1) of C₆D₆ has been analysed as well, from which improved values of the band origin and of the B and D _j constants of the excited states have been obtained. The strongest hot bands accompanying these parallel transitions have been assigned by means of the anharmonic force field calculated by Maslen et al. [1992, J. chem. Phys., 97, 4233]. In particular (ν₁₁ + ν₁₆) ? ν₁₆ is assigned to the band at 492.4 cm^?1 even though its shape is typical of a perpendicular transition (PAPE). New values for the ν₅, ν₁₂ and ν₁₆ band origins are determined from the band origins of combination bands and from calculated anharmonic constants. Numerous anharmonic constants are derived from the assignment of hot band and combination transitions.     

Observation of the v = 1 ← 0 band of SH (X2Π) with a difference frequency laser

The fundamental vibration-rotation band of SH (X²Π) has been studied in absorption at Doppler-limited resolution with an estimated accuracy of 0.002 cm^?1. The band origin (ν₀ = 2598.7675 ± 0.0003 cm^?1) and the molecular constants for the excited vibrational state (v = 1), as well as improved molecular constants for the ground vibrational state, have been determined in a least-squares fit.     

High resolution Fourier transform infrared spectroscopy on CH2DI and CHD2I: evaluation of the ground state constants and analyses of the C-I stretching bands ν3

Abstract

The high resolution (0.0010cm^?1) Fourier transform infrared spectra of the partially deuterated methyl iodide molecules CH₂DI and CHD₂1 have been recorded and analysed in the ν₃ band regions around 510cm^?1. The fundamental band ν₃ is associated with the stretching of the C-I bond and the spectra appear therefore as an asymmetric rotor hybrid a/b-type band and hybrid a/c-type band for CH₂DI and CHD₂I, respectively. About 4700 transitions in the case of CH₂DI and about 3900 transitions in the case of CHD₂I have been assigned. The ground state rotational constants of CH₂DI and CHD₂I have been obtained using the ground state combination differences calculated from the assigned ν₃ transitions and 16 microwave transitions from literature. The S reduced Watson's Hamiltonian has been used in the calculations. In addition, the upper state parameters describing the v₃=1 vibrational states of these molecules have been determined. The obtained ground state constants as well as the upper state parameters have been compared to the corresponding constants of the symmetric top species CH₃I and CD₃I     

High-resolution FTIR spectroscopy of the v11 and v2 + v7 bands of ethylene-d4

The Fourier transform infrared spectrum of the v₁₁ band of ethylene-d₄ (C₂D₄) has been recorded with an unapodized resolution of 0.006 cm^?1 in the frequency range 2150 to 2250cm^?1. The v₁₁ band, with a band centre of about 2201 cm^?1, was found to be perturbed by the nearby v₂ + v₇ band centred at about 2235 cm^?1 by a b-type Coriolis interaction. By fitting a total of 772 infrared transitions of v₁₁ using a Watson's A-reduced Hamiltonian in the I^r representation with the inclusion of b-type Coriolis interaction term, two sets of constants, up to quartic distortion constants for the v₁₁ = 1 state, and principal rotational constants for the v₂ + v₇ = 1 dark state, were derived. The inertia defect of the v₁₁ state was found to be 0.0693 ± 0.0004u Ų.     

Temperature Effect on the IR Absorption Spectra of Hydrogen Bonded (N[sbnd]…N)+ Homoconjugated Cations

Abstract

The effect of temperature on the absorption spectra from 50 to 3200 cm^?1 of a number of amine semiperchlorates and perchlorates of amines with two basic centres in which the hydrogen bridges (N [sbnd] H…N)⁺ are formed, was investigated. Three broad absorption regions may be distinguished in the spectrum, viz., between 100 and 900 cm^?1, 600 and 1800 cm^?1 and 1700 and 2900 cm^?1. The latter one may be assigned to the stretching vibration ν_S (N [sbnd] H…N).

A shift of this band peak (which is usually a doublet at room temperature for aromatic amines) towards longer wavelengths on decreasing the temperature may be an evidence that the bridge becomes shorter. Simultaneously with these changes, most salts under investigation exhibit a strong increase in low-frequency absorption intensity at about 400–600 cm^?1. It may be suggested that this absorption results from a transition between the split levels of the zero vibrational state.     

High resolution infrared study of the parallel band ν3 of chloroform CH35 Cl3

The infrared spectrum of chloroform in the region of the parallel fundamental band ν₃ around 367 cm^?1 has been measured with a Fourier spectrometer at a resolution of 0.001 cm^?1. An isotopically pure sample of CH³⁵Cl₃ was used. More than 5000 lines were assigned in the ν₃ band. A reanalysis of the ground state constants was performed by combining 1671 combination differences from this work, 712 differences from a previous study of the ν₂ band, and 80 millimetre wave lines from the literature. In the analysis of the ν₃ band, a model of an unperturbed symmetric top band was applied. The data were fitted with a standard deviation of 0.18 × 10^?3 cm^?1, and the following leading parameters were obtained: ν₀ = 367.295 550(8) cm^?1, B ₃—B ₀ = ?77.058(4) × 10^?6 cm^?1 and C ₃—C ₀ = ?18.600(11) × 10^?6 cm^?1. In addition, several hot bands have been studied. The isotopic effects were studied also by analysing spectra of the isotopically natural sample.     

Doppler-limited dye laser excitation spectroscopy of HCCl

The cw dye laser excitation spectrum of the $\text{A}\text{?}{}^1\text{A″(050) ←}\text{X}\text{?}{}^1\text{A′(000)}$ vibronic band of HCCl was observed between 16 539 and 16 656 cm^?1 with the Doppler-limited resolution, 0.03 cm^?1. The HCCl molecule was generated by the reaction of discharged CF₄ with CH₃Cl. The observed spectra were assigned to c-type transitions with ΔK_a = ±1 and also to axis-switching transitions with ΔK_a = 0 or ?2, but all with K′_a = 0, both for HC³⁵Cl and HC³⁷Cl. A rotational analysis yielded the rotational constants and quartic centrifugal distortion constants for the ground vibronic state and the band origin. A weak vibronic band, about one-third as intense as the main band, was found at about 57 cm^?1 to the violet of the main band for both isotopic species, and was ascribed to a transition from the ground vibronic state to a vibrational level, possibly (041), of the à state. The rotational levels of HC³⁵Cl in the à state showed a large perturbation; the J′ = 8, 9, and 10 levels were found to be split into two components. A normal coordinate analysis was carried out to calculate the centrifugal distortion constants and the inertia defect, which were in fair agreement with the observed values. The molecular structure of HCCl in the ground vibronic state was recalculated from the rotational constants of the two isotopic species combined with the 0.75B₀ + 0.25C₀ value previously reported for DC³⁵Cl.     

The CC stretching band ν6 of allene-d4

The infrared spectrum of C₃D₄ was measured in the region of the paralled band of the CC stretching vibration ν₆ centered at ν₀ = 1920.2332 cm^?1 on a high-resolution Fourier transform spectrometer and deconvolved to a linewidth of $\text{～}\text{1}\text{2}$ of the Doppler width (～0.0023 cm^?1). The high resolution reveals the presence of strong perturbations in the K = 4 and K = 8 to 12 levels of the ν₆ upper state. For a quantitative treatment of the observed transitions, a Hamiltonian matrix including six different perturbing states was constructed and used to refine the 6 spectroscopic constants of the ν₆ state and 20 of the constants for the perturbing states. Measurement of the hot band ν₆ + ν₁₁ ? ν₁₁ whose band center is at 1916.200 cm^?1 yielded the anharmonic constant x_6,11 = ?4.033 cm^?1.     

High-resolution infrared spectrum of CH2D2: The ν9 fundamental band at 8 u̧m

The infrared spectrum of CH₂D₂ has been recorded between 1100 and 1360 cm^?1 with a SISAM-type spectrometer whose resolution limit is about 0.015 cm^?1 in our spectrum. Some lines have been identified as transitions of the ν₃ parallel band of CH₃D. The band center ν = 1236.2786 ± 0.0010 cm^?1 and a set of upper state constants was obtained for the ν₉ band of CH₂D₂. A perturbation was pointed out in ν₉; nevertheless, all frequencies have been fitted with a standard deviation of 3.8 × 10^?3 cm^?1.     

High-resolution measurement and analysis of the infrared spectrum of nitric acid near 1700 cm−1

The infrared spectrum of the ν₂ band of nitric acid (HNO₃) has been measured with a tunable diode laser in the frequency interval from 1690 to 1727 cm^?1. A total of 430 assigned transitions have been analyzed to yield a set of nine rovibrational constants for the upper state with a standard deviation of 0.0012 cm^?1. The band is primarily B type with a band center at 1709.568 ± 0.005 cm^?1. Because of the absence of perturbations, the band constants can be used to calculate transition frequencies and relative intensities with a high degree of accuracy.     

Vibration-rotation bands in ethane

The absorption spectrum of ethane was recorded at 0.014 cm^?1 resolution in the range 4500–6500 cm^?1 using a Fourier transform spectrometer and at room temperature. Eighteen bands could be identified and their type assigned. Upper state rotational constants are provided for the band at 5948.338 cm^?1 and Coriolis constants are obtained for most perpendicular bands. Vibrational assignments are suggested for the bands at 5948 cm^?1 (v7 + v10), 5914 cm^?1(v8 + v ₁₀+ v ₁₁), and 5852cm^?1 (v ₅+v ₁₀). All vibrational bands reported in the literature are gathered.     

Rotational study and hyperfine effects of the (0,0) band of the B2Σ-X2Σ system of ScS

Rotational analysis of the (0,0) band of the B²Σ-X²Σ transition of ScS is reported. Spectrographic illustration of a hyperfine coupling transition in the ground state is demonstrated for the first time. This enables an order of magnitude to be obtained for γ″ (～0.003 cm^?1). The results for the other constants were: X state: B″ = 0.1971 cm^?1, D″ = 5 × 10^?8cm^?1, 4b = 0.23 cm^?1 (equal to that for ScO within the limits of measurement uncertainty); B state: B′ = 0.1853 cm^?1, D′ = 6 × 10^?8cm^?1, γ′ = ?0.0594 cm^?1, which can be compared with p_A²Π = 0.060 cm^?1. It was found that the two excited states A²Π and B²Σ constitute an excellent example of pure precession (p_pp = 0.058 cm^?1, and this enables the vibrational levels of A²Π to be numbered.     

High-resolution infrared spectrum of the ν2 + ν3 band of 14N16O2

The ν₂ + ν₃ band of ¹⁴N¹⁶O₂ has been recorded with resolution of 0.028 cm^?1. Ground state and upper state rotational constants have been obtained. The band center obtained, ν₀ = 2355.1517 ± 0.0011 cm^?1 (error cited is 3σ), has been combined with the band centers recently determined for ν₃ and ν₂ to calculate X₂₃ = ?11.348 ± 0.020 cm^?1 where the uncertainty cited is based on reasonable estimates of the absolute frequency error.     

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.     

Single crystal polarized Raman spectra of the solid electrolyte Cu2HgI4; attempt frequencies for ion motion in Ag2HgI4

The polarized Raman scattering from small single crystals of Cu₂HgI₄ provided assignments for the more prominent Raman features to specific irreducible representations. The E symmetry assignment, mass dependence, and pressure dependence of the 36 cm^?1 band in Cu₂HgI₄ and 24 cm^?1 band in Ag₂HgI₄ indicate that these features approximate the attempt frequency for ion hopping. The unusually high pre-exponential factor in the Arrhenius expression for ion hopping is discussed in light of the observed attempt frequency; we conclude that despite the high activation energy the conduction mechanism is similar to other heavy-metal solid electrolytes.     

Absorption spectrum of trideuteromethane between 7 and 11 μm. Analysis of the ν5 band

The absorption spectrum of trideuteromethane was recorded in the range 900–1400 cm^?1 with a resolution of 0.020–0.025 cm^?1. The ν₅ band centered at 1292.499 cm^?1 is analyzed here. A fit based on 869 observed transitions including J′ values up to 22, leads to a set of spectroscopic constants suitable for energy calculations in the upper-state v₅ = 1. These constants reproduce the experimental wavenumbers with a standard deviation equal to 0.008 cm^?1. The tabulated line strengths are calculated on the basis of the value S = 27.1 cm^?2 atm^?1 at 300 K, measured by Hiller and Straley, for the band strength of ν₅. A useful comparison is made between the values now derived for some constants and the corresponding ones predicted by Gray and Robiette in their recent force field calculations of methane and isotopic species.     

The Electronic Absorption Spectrum of Hafnium Monochloride

Abstract

Intracavity laser spectroscopy has been applied for investigation of absorption spectrum of HfCl molecule. In the region 560–700 nm 59 bands have been obtained. Rotational structure analysis of 0–0 band indicated that Hund's case (c) of angular moment coupling applied to this molecule. The molecular constants (cm^?1) calculated for upper and ground electronic states are: ω′ = 353.05 cm^?1, ω″ = 379.65 cm^?1, B′=0.21486 cm^?1 B″ = 0.21801 cm^?1.     

Far IR transmission spectra of an YBa2Cu3O7−δ thin film

Abstract

The FIR transmission of an YBa₂Cu₃O_7-δ film 1000 Å thick deposited on an MgO plate has been studied from 20 cm^?1 to 4000 cm^?1 at T = 300 K, and at 120 K, 80 K and 7 K. i) The spectra for the normal state are well fitted if a mid-IR oscillator of high strength and high damping is added to the simplest Drude model. ii) The spectra for the superconductive state do not show significant variations of transmission vs. temperature for ω > 120 cm^?1, which should be in agreement with a weak BCS coupling 2Δ = 3.5 kT_c . iii) The FIR transmission at 7 K for ω = 20 cm^?1 is not zero (around 1%) and seems to confirm that the low-temperature perovskite is made of two phases: a superconducting, and a normal one, the proportion of the first one increasing when the film temperature is decreased.     

EPR and optical absorption of manganese doped BaF2 and SrF2

Abstract

Mn⁺ ions in off-centre position along [100] have been produced in BaF₂:Mn by X-irradiation at LNT. Their EPR spectra are characterized by g-2. 0107. D = 265.8·10^?4cm^?1. A = 122.9·10^?4cm^?11 and a superhyperfine structure arising from 8 surrounding F^? nuclei. In the optical absorption spectrum they show up by a band at 411 nm. This behaviour is compared with the results found for SrF₂:Mn. After X-irradiation at room temperature beside a different Mn⁺ centre two species of Mn⁰ appear in non-cubic position. Both interact dominantly with two F^? neighbours. Possible models for these species are discussed.