Coherent Stokes and anti-Stokes Raman spectra of the ν1 (A1) and ν2 (E) bands of SF6 and UF6

Coherent Stokes and anti-Stokes Raman scattering are used to study the ν₁ and ν₂ spectral band profiles of UF₆ and SF₆. Most of the observed SF₆ “hot” bands are assigned, leading to evaluations of the anharmonicity constants X_ij: X₁₂ = ?(2.80 ± 0.30) cm^?1, X₁₄ = ?(1.00 ± 0.15) cm^?1, X₁₅ = ?(1.00 ± 0.15) cm^?1. For UF₆, a tentative assignment of the “hot” bands is made: X₁₂ = ?(1.80 ± 0.30) cm^?1, X₁₃ = ?(1.60 ± 0.30) cm^?1, X₁₄ = ?(0.20 ± 0.10) cm^?1, X₁₅ = ?(0.25 ± 0.10) cm^?1, and X₁₆ = ?(0.10 ± 0.05) cm^?1. Parameters such as the vibration-rotation coupling constants are determined. For SF₆: α = (7 ± 2) × 10^?5 cm^?1 for the ν₂ band and α = ?(1.02 ± 0.01) 10^?4 cm^?1 for the ν₁ band. The calculated spectral profiles of the coherent Stokes or anti-Stokes spectra, which are in good agreement with experimental results, give values for the resonant and nonresonant parts of the susceptibility in both molecules. They also show, in some cases, the influence of neighboring combination bands.     

Absorption of H and D Ly-α radiation by O2 molecules at high temperatures

Absorption cross sections of molecular oxygen were measured at the H and D Ly-α wavelengths (1215.67 and 1215.34 Å) between 800 and 1700°K, the cross sections being given by the equation σ (cm²) = 4.2E-18 exp(-3070/T) (4.2E-18 = 4.2 × 10^-18). The absorption cross section for v = 1 is (9±2)E-19 cm² and that for v = 2 is (7±3)E-18 cm², compared to 1.E-20 cm² for v = 0. Vibrational relaxation times were found to be in agreement with literature data over the range of common temperatures.     

The vibrational numbering and improved constants of the A3Π1u state of I2

The A-X system of I₂ has been recorded in absorption, under conditions of medium resolution, over the region 8000 – 13 400 Å. Bandheads in progressions based on v″ = 6 through 18 have been measured and assigned. A new vibrational numbering for the A state is proposed, which leads to more reliable values for the important constants of the A state: T_e = 10 906 ± 3 cm^?1, D_e = 1641 ± 3 cm^?1, ω_e = 92.5 ± 0.5 cm^?1, ω_ex_e = 1.20 ± 0.08 cm^?1, ω_ey_e = ?0.062 ± 0.006 cm^?1.     

ESR line shift in NiSnCl6·6H2O at very low temperatures

Electron spin resonance in a single-ground-state magnet, NiSnCl₆·6H₂O, has been studied at temperatures between 83 mK and 4.2 K. Below 1 K, the resonance lines show marked shifts, which can be described quantitatively in terms of exchange shift due to polarization effects treated by McMillan and Opechowski. The shifts give 2J = ?(0.55 ± 0.15) × 10^?2 cm^?1 for the antiferromagnetic exchange interaction among the Ni²⁺ ions in this crystal. The value of 2J is sub-critical in the sense that no spontaneous long-range order can be expected in this singlet-ground-state magnet.     

Spektroskopische Untersuchungen an DyAsO4

DyAsO₄ undergoes a crystallographic phase transition atT _D=11.2K which is induced by a cooperative Jahn-Teller-effect. As deduced from the optical absorption spectra the distance between the two lowest lying Kramers doublets of the Dy³⁺ ion is increased from (6.1±0.5) cm^?1 aboveT _D to (25.0±0.5) cm^?1 at 4.2 K. BelowT _D the splitting factor of the lowest doublet becomes nearly uniaxial with a maximum value ofg _b =17.5±1.0 along the crystallographicb-axis. AtT _N=2.44 K the crystals order antiferromagnetically. The absorption lines of Er³⁺ ions in DyAsO₄ show already a splitting immediately belowT _D which is explained by magnetic short range ordering of the Dy³⁺ ions in the temperature rangeT _{N D} .     

Torsion of the nitro group in nitroethylene

Eight NO₂-torsional transition frequencies obtained from interferometric far infrared measurements are reported. These data provide accurate information on the potential function for torsional angles up to 50°. The potential parameters are V₂ = 1642.7 ± 3.9 cm^?1 and V₄ = ?88.0 ± 1.7 cm^?1 for a rigid frame/rigid top model and V₂ = 1690.6 ± 4.2 cm^?1 and V₄ = ?90.8 ± 1.8 cm^?1 for a refined model allowing for distortions of the NO₂-group upon torsion. V₆ and V₈ terms are not significant.     

The geometry and forcefield of acetylene

The variational method has been used to determine the geometry and ground state potential surface of acetylene. All the parameters were refined through a least-squares fit to J = 0, 1 levels for C₂H₂ and C₂D₂. A new program was written to evaluate the rovibrational energy levels; in particular, primitive basis sets were developed for all values of J taking into account the singularity for linear geometries. Thus Σ, II, δ states can be refined. The full theory for tetraatomic linear molecules is presented. In this refinement 150 observed levels were used as data, below 10 000cm^?1. The geometry was refined and gives R_e(CC) = 1.2028 Å, R_e(CH) = 1.0618 Å, to be compared with the best experimentally derived values of 1.2027 ± 0.0005 Å, 1.062 ± 0.001 Å, respectively. The zero point energies are 5771.1cm^?1 for C₂H₂ and 4571.1cm^?1 for C₂D₂.     

Tunable laser study of the ν10 + ν11 band of cyclopropane

Diode laser measurements of the ν₁₀ + ν₁₁ (l_tot = ±2) perpendicular band of cyclopropane have led to the assignments of roughly 600 lines in the 1880–1920-cm^?1 region. Most of the spectra were recorded and stored in digital form using a rapid-scan mode of operating the laser. These spectra were calibrated, with the aid of a computer, by reference to the R lines of the ν₁ + ν₂ band of N₂O. The ground state constants we obtained are (in cm^?1) B = 0.670240 ± 2.4 × 10^?5, D_J = (1.090 ± 0.054) × 10^?6, D_JK = (?1.29 ± 0.19) × 10^?6, D_K = (0.2 ± 1.1) × 10^?6. The excited state levels are perturbed at large J values, presumably by Coriolis couplings between the active E′(l_tot = ±2) and the inactive A′(l_tot = 0) states. Effective values for the excited state constants were obtained by considering only the J < 15 levels. The A₁-A₂ splittings in the K′ = 1 excited states were observed to vary as q_effJ(J + 1), with q_eff = (2.17 ± 0.17) × 10^?4 cm^?1.     

The analysis of symmetric rotor Raman spectra: The pure rotational spectrum of 11BF3

The pure rotational Raman spectrum of ¹¹BF₃ has been photographed. Great care was taken in the analysis to consider all the unresolved components under each observed Raman line profile. If this is ignored, systematic errors result. The final set of molecular constants obtained was B₀ = 0.34502(±3 × 10^?5)cm^?1, D_J = 4.38(±0.10) × 10^?7cm^?1, and D_JK = ?9.1(±1.0) × 10^?7cm^?1.     

The ground-state rotational constants of germane

The ground-state rotational constants B₀, D₀, and H₀ have been determined for GeH₄ from the analysis of ground-state combination differences in the infrared spectra of isotopically enriched ⁷⁰GeH₄, ⁷²GeH₄, and ⁷⁴GeH₄. The spectra were recorded at 0.06-cm^?1 resolution and about 0.005-cm^?1 precision for unblended lines. Suitable combination differences were found in both the ν₂ and the ν₄ infrared bands. The ground-state constants were assumed to be invariant to isotopic substitution at Ge, and the tensor distortion constants were held fixed at their microwave values. The results obtained are: B₀ = 2.69587 ± 0.00007 cm^?1, D₀ = (3.34 ± 0.03) × 10^?5 cm^?1, H₀ = (1.3 ± 0.5) × 10^?9 cm^?1.     

Ethane spectrum between 1940 and 2152 cm−1: Ground state parameters

The absorption spectrum of ethane was recorded between 1940 and 2152 cm^?1 at a resolution of 0.025 cm^?1. Ground state parameters were determined from the principal band in this region, ν₉ + ν₁₂(E_u): B₀ = 0.6630353 cm^?1, D₀^J = 1.0406 × 10^?6 cm^?1, D₀^JK = 2.575 × 10^?6 cm^?1 (standard errors are 7, 8, and 13, respectively, in the last digits quoted). The quoted values are from the analyses of 269 ground state combination differences, the standard deviation of the least-squares analysis was 0.0032 cm^?1.     

Mößbauereffekt in FeCl2, FeSO4 und FeSO4 · 7 H2O

Mößbauereffect measurements were performed with FeCl₂, FeSO₄ and FeSO₄ · 7 H₂O in the temperature range between 5 and 300 ?K. The quadrupole splittings at 5 ?K were determined to be (1.300±0.027) mm/sec, (3.650±0.053) mm/sec, and (3.350±0.053) mm/sec respectively. From the temperature dependence of the quadrupole splittings it follows that in FeCl₂ the energy of the excited 3d-electron-level isδ=150 cm^?1, in FeSO₄ δ ₁=360 cm^?1 andδ ₂=1680 cm^?1 and in FeSO₄ · 7 H₂Oδ ₁=480 cm^?1 andδ ₂=1300 cm^?1. The magnitudes of the magnetic field at the iron nucleus at 5 ?K are (202±8) kOe for FeSO₄ and (0±4) kOe for FeCl₂.     

Pressure broadening of UF6 by argon

Pressure broadening of the R(6) manifold in ν₃ of UF₆ at 628.32 cm^?1 has been measured at pressures of 0–30 torr of Ar in a long-path cell at 199 ± 1 K. We obtain a pressure-broadening coefficient of 9.0 ± 1.5 MHz/torr (FWHM), which corresponds to 7.3 ± 1.2 MHz/torr at 300 K. The UF₆-Ar optical collision diameter is 7.4 ± 0.6 Å; this is larger than the hard-sphere kinetic theory collision diameter of 5.2 Å obtained from the diffusion coefficient and implies rapid rotational relaxation.     

Isomer shift in BaSnO3 under a pressure up to 15 GPa

The dependence of the unit cell volume of BaSnO₃ on the pressure up to 15 GPa has been investigated and the constants of the Murnaghan equation of state B ₀ = 178.39 ± 4.09 GPa and B′₀ = 4.68 ± 0.56 have been obtained using the X-ray diffraction method. The change of the isomer shift (IS) in BaSnO₃ with a variation in the pressure P has been examined using the gamma resonance method. This quantity is ?IS(P)/?P = ?(0.00474 ± 0.0002) mm s^?1 GPa^?1 or, taking into account the measurements of the unit cell parameter under pressure, ?IS/?L = 1.42 mm s^?1Å^?1, where L is the tin-oxygen distance.     

An experimental study of the collisional broadening of the Na-D lines by Ar and N2 perturbers in flames and vapor cells—II. The line wings

In this paper, we report on measurements of the fluorescence-excitation profile of the red Na-D₁ line wing from about 1 cm^?1 to 1100 cm^?1 and of the blue Na-D₂ line-wing from about 1 cm^?1 to 600 cm^?1, with respect to the corresponding line centre. We have also measured the fluorescence-excitation profile of the red Na-D₂ and blue Na-D₁ inner (overlapping) line wings from 1 cm^?1 with respect to the centre of each of the lines. All these wings were measured in several premixed, laminar, shielded H₂O₂Ar and H₂O₂N₂ flames at 1 atm (1400 K ? T ? 2300 K). We also measured these wings in a vapor cell containing Ar or N₂ perturbers (T ～ 480 K, p ～ 0.4 atm) in order to determine the influence of temperature on these wings. Using a tunable CW dye laser as excitation source, we determined the fluorescence-excitation profiles by measuring the total fluorescence intensity while tuning the laser wavelength. In order to specify the contributions that the different kinds of major flame perturbers (Ar, N₂, H₂O) make to the wings, we compared the wing profiles measured in various flames of different flame-gas compositions. In this comparison, the wing profiles were normalized with respect to the line-centre. We compared our measurements of far red Na-D₁ and blue Na-D₂ line-wings ($\text{Δσ ? 30}\text{cm}{}^{\mathrm{?1}}$) specified to Ar perturbers (at T = 500 K and T = 2000 K) with the results derived from quasi-static theory using available interaction potential data. In the case of Ar perturbers at T = 500 K, we observed a satellite at about 8 cm^?1 from the line-centre on the red Na-D₁ wing: this satellite was absent at T = 2000 K. The position of this red satellite was explained with the help of a set of “modified” potentials, which were constructed for interpreting the collisional Na-D broadening- and shift-rates deduced from our line-core observations and which were reported in Part I of this paper.     

Infrared rotation-vibration spectra of ethane: The perpendicular band, ν7, of C2H6

The study of the gas-phase infrared spectrum of C₂H₆ in the region of the perpendicular CH-stretching band, ν₇, near 3000 cm^?1 is extended for the ΔK = + 1 subbands as far as K = 20. The spectral resolution of ～0.030 cm^?1 is increased to ～0.015 cm^?1 by deconvolution. The earlier investigation of this band for KΔK = +9 to ?5, is repeated with greater accuracy, providing more reliable ground-state constants (cm^?1): B₀ = 0.663089 ± 24, D₀^J = (0.108 ± 4) × 10^?5, D₀^JK = (0.50 ± 7) × 10^?5. The molecular constants (cm^?1) for the ν₇ fundamental are B₇ = 0.66310 ± 3, A₇ = 2.682, ν₀ = 2985.39, ζ₇ = 0.128. A discussion of resonance effects in this band, in particular x-y-Coriolis and Fermi resonance, is given.     

Noble gas halides: The B → X and D → X systems of 136Xe35Cl

The B → X (2870–3100 Å) and D → X (2250–2370 Å) band systems of ¹³⁶Xe³⁵Cl are photographed and vibrationally analyzed. A simultaneous least-squares fit of 41 band-heads in the B-X system and 35 in D-X yields, in part, the following constants (in cm^?1): T_eB = 32 405.8, T_eD = 42 347.9, ω_eB = 194.75, ω_eD = 204.34, ω_eX = 26.22. The ground state dissociation energy ($\text{D}$″_e) is estimated to be 281 ± 10 cm^?1. Potential curves are derived for all three states through Franck-Condon calculations. From these curves the D-state internuclear distance is 0.09 ± .02 Å smaller than the B-state distance.     

Intensities and half-widths at different temperatures for the 201III←000 band of CO2 at 4854 cm−1

Measurements made at temperatures of 197, 233, and 294°K of the absolute intensities and self-broadening coefficients for the vibration-rotation lines of the 201_III←000 band of the ¹²C¹⁶O₂ molecule, are reported. From these measurements, values have been derived for the vibration-rotation interaction factor (F_VR), the purely vibrational transition moment (|R(O)|), and the intensity (S_Band). The results are: E_VR(m) = 1+(2.2±0.7)×10^?3m+(5.6±1.6)×10^×5m², |R(0)| = (2.064±0.017)×10^?3 debye, S_Band = 21,329±69 cm^?1km^?1atm^?1_STP. The results for the self-broadening coefficients are presented in the text.     

Analysis of the ν6(A″2) band of cyclopropane-d6 recorded under high resolution

The parallel band ν₆(A″₂) of C₃D₆ near 2336 cm^?1 has been studied with high resolution (Δν = 0.020 – 0.024 cm^?1) in the infrared. The band has been analyzed using standard techniques and the following parameters have been determined: B″ = 0.461388(20) cm^?1, D″_J = 3.83(17) × 10^?7 cm^?1, ν₀ = 2336.764(2) cm^?1, α^B = (B″ ? B′) = 8.823(12) × 10^?4 cm^?1, β^J = (D″_J ? D′_J) = 0, and α^C = (C″ ? C′) = 4.5(5) × 10^?4 cm^?1.     

Determination of A0 for CH335Cl and CH337Cl from the ν4 infrared and Raman bands

The ν₄ infrared and Raman bands of CH₃Cl were analyzed simultaneously. A direct fit yielded a complete set of constants for CH₃³⁵Cl, including A₀ = 5.20530 ± 0.00010 cm^?1 and D_K = (8.85 ± 0.13) × 10^?5cm^?1. For CH₃³⁷Cl an incomplete set of constants was obtained from the infrared band, and A₀ = 5.2182 ± 0.0010 cm^?1 was estimated by curve fitting of the Raman spectrum. The resulting equilibrium structure is $\text{r(}\text{CH) = 1.0854 ± 0.0005}\text{A}\text{?}$, $\text{r(}\text{CCl) = 1.7760 ± 0.0003}\text{A}\text{?}$, and <(HCH) = 110°.35 ± 0°.05.