Vibration-rotation analysis of the jet-cooled v12, v7 + v8 and v6 + v10 absorption bands of 12C2H4

A Fourier transform interferometer was used to record the slit-jet cooled absorption spectrum of ¹²C₂H₄ between 700 and 2400 cm^?1I, at a spectral resolution of 0.005 cm^?1. Three bands, v₁₂ at 1442.442 70(1)cm^?1, v₇ + v₈ at 1888.978 23(3)cm^?1 and v₆ + v₁₀ at 2047.775832(2)cm^?1, were rotationally analysed. In the case of 7¹8¹, a known Coriolis perturbation mechanism involving the nearby 4¹8¹ (1958.264cm^?1) and 8¹10¹ (1766.391 cm^?1) states was accounted for in the analysis. The latter fitting procedure included 12 levels from the 4¹8¹ state which are observed because lines from v₄ + v₈ borrow intensity from v₇ + v₈. Compared to the literature, significantly improved vibration-rotation constants were obtained for all upper states reported in the present study.     

Anharmonic resonances between the v 1 + v ±1 6, v 3 + v ±1 5 + 2v 0 6 and v 3 + v ∓1 5 + 2v ±2 6 vibrational bands of CH3 79Br

The 22 K sub-bands, belonging to the v ₁ + v ^±1 ₆, v ₃ + v ^± ₅ + 2v ⁰ ₆ and v ₃ + v ^±1 ₅ + 2v ^±2 ₆ rovibrational bands of monoisotopic CH₃ ⁷⁹Br, have been identified. An RMS standard deviation of about 0·020 cm^-1 has been achieved by a least squares fit over 619 lines belonging to these 22 sub-bands. For this purpose, a model taking into account (a) anharmonic resonances between (i) v ₁ + v ^±1 ₆, and v ₃ + v ^±1 ₅ + 2v ⁰ ₆, (ii) v ₁ + v ^±1 ₆ and v ₃ + v ^?1 ₅ + 2v ^±2 ₆ and (iii) v ₃ + v ^±1 ₅ + 2v ⁰ ₆ and v ₂ + 2v ₃ + v ^±1 ₅ and (b) Coriolis resonances between the v ₂ and v ₅ modes, was used.     

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.     

EPR study of Fe3+ and Mn2+ in CeO2 and ThO2

Attempts were made to grow CeO₂ and ThO₂ single crystals doped with transition metal ions. Only Fe³⁺ and Mn²⁺ could be detected by the EPR technique. The EPR spectrum of Fe³⁺ in CeO₂ exhibits the well-known fine structure in cubic fields. The parameters areg=2.0044(1) anda=15.6(1)·10^?4 cm^?1. The hyperfine constantA for⁵⁷Fe in hexahedral coordination was found to be 8.9(1)·10^?4 cm^?1. The EPR spectrum of Mn²⁺ in CeO₂ reveals two cubic Mn²⁺ centers. The parameters for center 1 areg=1.9999(1) andA=86.9(1)·10^?4 cm^?1 and for center 2g=1.9984(1) andA=87.0(1)·10^?4 cm^?1. Heating the Mn doped CeO₂ samples in hydrogen, the Mn²⁺ centers transform from cubic into trigonal centers with approximate values ofg=1.9988(2),A=84.5(6)·10^?4 cm^?1 andD=203(1)·10^?4 cm^?1. The two observed Mn²⁺ centers in ThO₂ exhibita priori axial symmetry with approximate values ofg=2.0006(2),A=88.9(4)·10^?4 cm^?1 andD=33(3)·10^?4 cm^?1.     

Etude rovibrationnelle de la bande parallèle à structure perpendiculaire v 4 + v 6 de CH3 35Cl

La bande infrarouge v ₄ ^±1 + v ₆ ^?1 de CH₃ ³⁵Cl, centrée vers 4051 cm^-1, a été analysée sur un spectre de 0,0075 cm^-1 de résolution. On a mis en évidence une résonance l vibrationnelle de couplage R = -2,5 cm^-1, et une résonance anharmonique de couplage W _F ～4,86 cm^-1 avec la bande 4v ₆ ⁰ centrée vers 4049 cm^-1; par suite de la proximité des deux centres de bande, cette résonance est forte et fait apparaître la sous-bande K = 0 de 4v ₆ ⁰. Un calcul de moindres carrés sur 813 raies a donné un écart standard de 0,020 cm^-1, de petites anomalies rotationnelles restant à élucider.     

Infrared diode-laser spectrum of the CH3CN ν2 band: Analysis of local resonances with ν6±1 + 2ν8±2, ν4 + ν7±1 + ν8±1, ν4 + ν6±1, ν4 + ν7±1, and 2ν70 + ν8±1 states

Fifty-one sections of infrared diode-laser spectra of acetonitrile have been measured in the region from 2283.5 to 2235.7 cm^?1. About 450 transitions belonging to the ν₂ band have been assigned for K ≦ 7 and J ≦ 44. Anomalies found in the rotational structure have been proven to be due to five local resonances. Observed transition frequencies have been fitted by a least-squares method to a model which includes Fermi-type resonances (Δk = 0, Δ? = ± 3n) with ν₆^±1 + 2ν₈^±2 and ν₄ + ν₇^±1 + ν₈^±1 states, x, y-type Coriolis resonances (Δk = ±1, Δ? = ?3n ± 1) with ν₄ + ν₆^±1 and ν₄ + ν₇^±1 + ν₈^±1 states, and a centrifugal-distortion-type resonance (Δk = ±2, Δ? = ?3n ± 2) with a 2ν₇⁰ + ν₈^±1 state. The 11 × 11 dimensional energy matrix has been diagonalized in order to obtain the perturbed energy levels. The standard deviation for the fit is 1.075 × 10^?3 cm^?1. The molecular constants determined are also listed.     

High resolution study of the v 7 + v 8 band of ethylene (C2H4) at 1889 cm-1

The v ₇ + v ₈ A-type band of C₂H₄ has been recorded between 1932 and 1847 cm^-1 with a resolution of 0·06 cm^-1. The transitions with K _-1 ? 8> and J ? 2>5 have been assigned. Although slight Coriolis resonances perturb the band, the analysis has been made easy through the use of an elaborate set of asymmetric top computer programmes. The band centre and a set of upper state constants have been obtained. With these constants, 288 observed upper state energy levels have been fitted with a standard deviation of 0·021 cm^-1.

Using very simple expressions, we have predicted all the resonance effects perturbing the levels of ethylene near 2000 cm^-1. This led us to the identification of the v ₄ + v ₈ and v ₈ + v ₁₀ combination bands in low resolution spectra.     

Experimental determination of the potential energy curves of the I(3/2u) and I(3/2g) states of Kr+ 2

The I(3/2u) and I(3/2g) states of Kr⁺ ₂ have been investigated by pulsed-field-ionization zero-kinetic-energy (PFI-ZEKE) photoelectron spectroscopy following (2 + 1′) resonance-enhanced multiphoton excitation via the 0⁺ _g Rydberg state located below the Kr?([4p]⁵5p[1/2]₀) + Kr(¹S₀) dissociation limit of Kr₂. From the positions of a large number of vibrational bands in the spectra of the ⁸⁴Kr₂ and ⁸⁴Kr-⁸⁶Kr isotopomers, the adiabatic ionization potentials (IP(I(3/2u)) = 112672.4 ± 0.8cm^?1, IP(I(3/2g)) = 111 395.0 ± 1.4cm^?1), the dissociation energies (D ⁺ ₀(I(3/2u)) = 368.8 ± 2.0cm^?1, D ⁺ ₀(I(3/2g)) = 1646.2 ± 2.3cm^?1) and vibrational constants for both ionic states have been determined. Potential energy curves have been extracted which perfectly reproduce all experimental observations and are accurate over a wide range of energies and internuclear distances. The equilibrium internuclear distances (R ⁺ _e(I(3/2u)) = 4.11 ± 0.04 Å, R ⁺ _e(I(3/2g)) = 3.35 ± 0.10 Å) have been derived by comparing the intensity distribution in the PFI-ZEKE photoelectron spectra to calculated Franck-Condon factors. The dissociation energy of the I(3/2g) state and the equilibrium internuclear distance of the I(3/2u) state differ markedly from previously reported values.     

Photoionization and photoelectron angular distribution for H2

Photoionization of H₂(¹Σ_g⁺) in a vibrational υ″ and rotational N″ state into H₂⁺(²Σ_g⁺) in a vibrational υ′ and rotational N′ state is studied theoretically. The differential cross section, after summing over the final states, is expressed in the well-known simple form of $\text{(}\text{σ}{}_{\mathrm{T}}\text{4π}\text{)[1 + βP}{}_2\text{(}\text{cos}\text{θ)]}$. Parallel expressions are obtained for H₂⁺ in a specific υ′ state (in terms of σ(υ′) and β(υ′)) and for H₂⁺ in a rotational fine level υ′N′ (in terms of σ(υ′N′) and β(υ′N′)). Asymmetry parameters β, β(υ′) and β υ′N′), which are expressed in terms of Racah and Clebsch-Gordan coefficients and electronic transition moments, can be reduced approximately to 2 lineary polarized light and to -1 for unpolarized light. Using single-center electronic wave functions and including partial eaves l = 1, 3, and 5, σ(υ′) and β(υ′) are computed as a function of υ′ at 584 Å. The computed σ(υ′) divided by the Frank-Condon overlap, in agreement with experimental results, increases monotonically with υ′; σ_T and β are computed in the incident photon energy range of 600–4000 Å and the results compare favorably with previous calculations.     

A Vibrational Spectroscopic Study of the So-Called Healing Mineral Papagoite CaCuAlSi2O6(OH)3

ABSTRACT

Papagoite is a silicate mineral named after an American Indian tribe and was used as a healing mineral. Papagoite CaCuAlSi₂O₆(OH)₃ is a hydroxy mixed anion compound with both silicate and hydroxyl anions in the formula. The structural characterization of the mineral papagoite remains incomplete. Papagoite is a four-membered ring silicate with Cu²⁺ in square planar coordination.

The intense sharp Raman band at 1053 cm^?1 is assigned to the ν₁ (A _1g) symmetric stretching vibration of the SiO₄ units. The splitting of the ν₃ vibrational mode offers support to the concept that the SiO₄ tetrahedron in papagoite is strongly distorted. A very intense Raman band observed at 630 cm^?1 with a shoulder at 644 cm^?1 is assigned to the ν₄ vibrational modes.

Intense Raman bands at 419 and 460 cm^?1 are attributed to the ν₂ bending modes.

Intense Raman bands at 3545 and 3573 cm^?1 are assigned to the stretching vibrations of the OH units. Low-intensity Raman bands at 3368 and 3453 cm^?1 are assigned to water stretching modes. It is suggested that the formula of papagoite is more likely to be CaCuAlSi₂O₆(OH)₃ · xH₂O. Hence, vibrational spectroscopy has been used to characterize the molecular structure of papagoite.     

Growth,spectral and laser properties of Nd3+:Na2La4(WO4)7 crystal

A Nd³⁺:Na₂La₄(WO₄)₇ crystal with dimensions of ? 17 × 30 mm³ was grown by the Czochralski method. The thermal expansion coefficients of Nd³⁺:Na₂La₄(WO₄)₇ crystal are 1.32 × 10^?5 K^?1 along c-axis and 1.23 × 10^?5 K^?1 along a-axis, respectively. The spectroscopic characteristics of Nd³⁺:Na₂La₄(WO₄)₇ crystal were investigated. The Judd–Ofelt theory was applied to calculate the spectral parameters. The absorption cross sections at 805 nm are 2.17 × 10^?20 cm² with a full width at half maximum (FWHM) of 15 nm for π-polarization, and 2.29 × 10^?20 cm² with a FWHM of 14 nm for σ-polarization. The emission cross sections are 3.19 × 10^?20 cm² for σ-polarization and 2.67 × 10^?20 cm² for π-polarization at 1,064 nm. The fluorescence quantum efficiency is 67 %. The quasi-cw laser of Nd³⁺:Na₂La₄(WO₄)₇ crystal was performed. The maximum output power is 80 mW. The slope efficiency is 7.12 %. The results suggest Nd³⁺:Na₂La₄(WO₄)₇ crystal as a promising laser crystal fit for laser diode pumping.     

Line strengths,spin-splittings,and forbidden transitions in the (101) band of 14N16O2

Measurements of line strengths in the (101) and (111)-(010) bands of ¹⁴N¹⁶O₂ have been made at a resolution of 0.02 cm^?1 in the region 2863 to 2934 cm^?1. The strength data in the (101) band were analyzed to determine a vibrational band strength and coefficients of the F factor. Each subband for K_?1 ≤ 9 was analyzed separately and all the F-factor coefficients in terms of the rotational quantum number, N, were found to be too small to be of significance. However, F was found to be dependent on K_?1 and the experimentally determined subband strengths were least-squares fitted to the expression S_v⁰·F, where S_v⁰ = 68.3 cm^?2 atm^?1 at 296 K and F = 1 + (2.899 × 10^?3)K_?1 + (4.08 × 10^?3)K_?1² ? (2.34 × 10^?4)K_?1³. The integrated strengths for the (101) and (111)-(010) bands were found to be 70.9 ± 2.3 and 2.7 ± 0.3 cm^?2 atm^?1 at 296 K, respectively. Also included in this study are measurements of line center positions in the two bands and spin-splittings in the (101) band. Recent frequency measurements of lines with K_?1 ≤ 8 in the (101) band have been made at a resolution of 0.0033 cm^?1 by V. Dana and J. P. Maillard (J. Mol. Spectrosc.71, 1–4) (1978)) for the region above 2889 cm^?1 and our values are in excellent agreement with theirs. Separations of the split lines measured in this work (K_?1 ≤ 10) agree well with calculated values using expressions which include the η_aaaaK_?1⁴ term with η′_aaaa = ?1.70 ± 0.15 × 10^?4 cm^?1 as derived for the (101) state. Three forbidden (ΔN ≠ ΔJ, ΔK_?1 = 0) transitions in the (101) band were observed with their identifications based on the agreement between measured and calculated line positions and strengths.     

Supertransferred hyperfine structure in EPR of V4+ ion in Ca3In2Ge3O12 garnet

Interaction of an unpaired electron of the tetrahedral V⁴⁺ ion in Ca₃In₂Ge₃O₁₂ garnet with the four nearest In nuclei gives rise to clearly resolved structure of EPR spectra. We report the observation and analysis of these spectra at three frequencies and at temperature 77 K. The temperature dependence between liquid helium and the room temperatures was also studied. Parameters of the spin Hamiltonian are g_∥=1·8735; g_⊥=1·9825; ∣ ¦A∥|=150·4×10^?4cm^?1; ¦ A_⊥¦ = 36·7 × 10^?4 cm^?1. The supertransferred hyperfine interaction was found to be isotropic, absolute value of the corresponding parameter a is 22·1 × 10^?4 cm^?1.     

Negative Ions,Ozone, and Metastable Components in dc Oxygen Glow Discharge

In a dc glow discharge in oxygen, the concentrations of minor components of O₂(a¹Δ_g), O₂(b¹ Σ_g), O₃, O(¹D), as well as nagative ions and electrons have been measured. Balance equations have been derived which describe satisfactorily the stationary concentrations of these components as functions of gas pressure and discharge current. For the first time, the rate constants of important aeronomical reactions (a) O^? + O₂(a¹Δ_g) → O₃ + e, (b) O₂^? + O₂(a¹Δ_g) → 2O₂ + e and (c) e + O₃ → O₂^? +O have been measured as functions of gas temperature T and mean energies of ions E_i and electron E₆: K_a = (2.5 ± 0.5) · 10^?9 · (T/300)^{4 ± 0.4}· (E_i/0.04)^{?2.6 ± 0.4} cm³/s for T = 385?605 K and E_i = 0.10 ? 0.66 eV; K_b = (1.0 ± 0.3) · 10^?10 · (T/300)^{?2 ± 0.5} · (E_i/0.04)^{0.23 ± 0.05} cm³/s for T = 330?605 K and E_i = 0.09 + 1.5 eV; K_c for E_e = 0.8÷5 eV.     

The infrared spectrum of 12C2HD: the bending states up to υ4 +υ5 =3

The infrared spectrum of ¹²C₂HD has been recorded at high resolution between 450 and 2100?cm^?1 by Fourier transform spectroscopy. The ν₄ and ν₅ bending fundamental bands together with overtones, combination bands and associated hot bands involving modes up to υ_tot?=?υ₄?+?υ₅?=?3 have been identified. Altogether, 43 vibrational bands have been analysed, leading to the spectroscopic characterization of the ground state and of 18 vibrationally excited states. They include all the components of the vibrational manifolds up to υ_tot?=?3, with the exception of the υ₄?=?3, ??=?±3 state. A simultaneous fit of all the assigned transitions has been performed. The adopted model includes vibration and rotation ?-type interaction resonances. The determined spectroscopic parameters reproduce the assigned wavenumber transitions with RMS values close to the estimated experimental uncertainties.     

Dipolar studies in CaF2 with Ce3+

Dielectric relaxation in CaF₂ doped with various amounts of Ce³⁺ (0·01 to 1·0 mol%) was measured. The value of the activation energy for orientation of the dipoles {Ce³⁺-F^? interstitial} was determined to be H = (0·46 ± 0·01) eV. The frequency factor was found to have the value τ_o = (5 ± 1) × 10^?15 sec, giving for the vibrational frequency of the interstitial the value ν_o = (5 ± 1) × 10¹³ sec^?1.The number of dipoles contributing to the dielectric loss peak was determined to be between 10¹⁷ and 8 × 10¹⁷ cm^?3 for the different doping amounts of Ce³⁺. Optical absorption measurements showed the existence of large aggregate bands. We could verify that there exists a second-order reaction of aggregation, which is responsible for the non-linearity found between optical absorption at 305 nm and the nominal concentration of Ce³⁺ in the samples. On the other hand, if we assume that the centers which contribute to optical absorption at 305 nm are those also responsible for the relaxation peak, we find that the number contributing to each process is not the same. We can define an interaction radius R as the minimum separation between two dipoles allowing them to contribute to the relaxation peak. From our experimental data R ? 3·8 × 10^?7 cm.     

High resolution FTIR spectroscopy of CH2DF: analysis of the v 3 and v 4 interacting bands

The high resolution (0.004cm^?1) Fourier transform infrared spectrum of the monodeuterated form of methyl fluoride, CH₂DF, has been recorded and analysed in the v ₃ and v ₄ band region around 1420cm^?1. Both bands, coming from A′ symmetry vibrations, have a/b hybrid character, although in v ₃ the b-type component prevails over the a-type. The rotational structure has been analysed using a dyad model including c-type Coriolis coupling and high order vibrational resonance between these states. Accurate upper state molecular parameters and interaction terms have been obtained by fitting about 3270 assigned transitions to Watson's A-reduced Hamiltonian in the I^r representation. In addition, from a simultaneous fit of ground state combination differences coming from this analysis and 42 literature microwave transitions, an improved and more complete set of ground state constants, including three new sextic centrifugal distortion terms (Φ_JK, Φ_KJ and Φ_K), has been derived.     

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.     

The ν6, ν8 3ν4+ν12 infrared system of Si2H6 under high resolution: rotational and torsional analysis

A Fourier transform infrared spectrum of disilane has been measured at a Doppler limited resolution, and analysed in the region of the ν₆ and ν₈ fundamentals, from about 800 to 1020cm^?1. The torsional splittings are not resolved in the ν₆ band, showing that the splittings in the ν₆ = 1 state and in the ground state are almost identical. The torsional splittings in the reasonably unperturbed regions of the ν₈ fundamental are about 0.0146cm^?1, and a detailed rotation-torsion analysis shows that the intrinsic splittings in the ν₈ = 1 state are smaller than in the ground state by this amount. An intrinsic torsional splitting about 0.0150 cm^?1 is estimated in the vibrational ground state and in the ν₆ = 1 state, and almost vanishing in the ν₈ = 1 state (about 0.0004cm^?1), with a barrier height around 407cm^?1. This is in agreement with the expectation from theory. The ν₈ band, beyond a moderate x, y-Coriolis coupling with ν₆, is affected by several perturbations, also selective in the torsional components. The 3ν₄ + v¹² combination, with three quanta of the torsional mode excited and large torsional splittings, is the main perturber, causing both Fermi and Coriolis resonances in several regions of the spectrum. The vibrational origins of all four torsional components of 3ν₄ + v¹² were determined. Other perturbative effects are attributed to the systems 2ν₃ + ν₄, and ν₄ + 24₉(E + A). The spectrum was numerically analysed, and the relevant vibration-rotation-torsion parameters were determined.     

Proton N.M.R. study of the dynamics of the ammonium ion in ferroelectric langbeinite, (NH4)2Cd2(SO4)3

The proton N.M.R. lineshape of polycrystalline Langbeinite, (NH₄)₂Cd₂(SO₄)₃, has been studied in the temperature range 300 K to 1·8 K. The resonance line is motionally narrowed over the entire temperature range, and the low temperature proton line shows clear evidence for tunnelling motion of the ammonium ion between spin-symmetry states. From a computer simulation of the lineshape, we obtain an estimate for the tunnelling splitting parameter, J, of the torsional ground state of the ammonium ion, as 375 ± 125 gauss. For an undistorted tetrahedral crystal field this corresponds to a tunnelling splitting Δ = 4J = 6·3 ± 2·1 MHz.

Pulsed proton N.M.R. studies have also been carried out on the above compound at 30·8 MHz and 48·2 MHz and the spin-lattice relaxation time (T ₁) has been measured by the π - t - π/2 pulse sequence as a function of temperature down to 77 K. At 30·8 MHz, a T ₁ minimum of 13 ms occurs at 105·8 K, and is ascribed to random reorientations of the NH₄ ⁺ ion. An activational energy barrier of 0·74 ± 0·1 kcal/mole and an associated pre-exponential factor of 8·0 × 10^-13 s are calculated for the above motional process, and the value of the activation energy is correlated with the tunnelling splitting of the torsional ground state.

An anomaly in T ₁ has been observed at the ferroelectric Curie point (95 K), indicating the order-disorder nature of the transition. This is the first experimental evidence relating to the nature of the transition in Langbeinite.