The ν3 and 2ν3 bands of SO3, SO3, SO3, and SO3

This sixth of a series of publications on the high-resolution rotation-vibration spectra of sulfur trioxide reports the results of a systematic study of the ν₃ and 2ν₃ infrared bands of the four symmetric top isotopomers ³²S¹⁶O₃, ³²S¹⁸O₃, ³⁴S¹⁶O₃, and ³⁴S¹⁸O₃. An internal coupling between the l=0(A₁^′) and l=2(E^′) levels of the 2ν₃ states was observed. This small perturbation results in a level crossing between |k−l|=9 and 12, in consequence of which the band origins of the A₁^′,l=0 “ghost” states could be determined to a high degree of accuracy. Ground and upper state rotational constants as well as vibrational anharmonicity constants are reported. The constants for the center-of-mass substituted species ³²S¹⁶O₃ and ³⁴S¹⁶O₃ vary only slightly, as do the constants for the ³²S¹⁸O₃, ³⁴S¹⁸O₃ pair. The S-O bond lengths for the vibrational ground states of the species ³²S¹⁶O₃, ³⁴S¹⁶O₃, ³²S¹⁸O₃, and ³⁴S¹⁸O₃ are, respectively, 141.981 99(1), 141.979 38(6), 141.972 78(8), and 141.969 93(8) pm, where the uncertainties, given in parentheses, are two standard deviations and refer to the last digits of the associated quantity.     

Analysis of high-resolution infrared and CARS spectra of SO3

Three fundamental modes and several hot bands of ³⁴S¹⁸O₃ have been investigated using both infrared spectroscopy and coherent anti-Stokes Raman scattering spectroscopy (CARS). Coriolis coupling effects are particularly noticeable in ³⁴S¹⁸O₃ due to the close proximity of the ν₂ and ν₄ fundamental vibrations, whose wavenumber values are 477.50864(5) and 502.05565(4) cm⁻¹. The uncertainties in the last digits are shown in parentheses and are two standard deviations. Hot band transitions from ν₂, ν₄ levels give access to infrared inactive ν₂, ν₄ combination/overtone levels which interact strongly with levels of the Raman-active ν₁ symmetric stretching mode due to indirect Coriolis couplings, l-resonances, and Fermi resonances. The result is a complex ν₁ CARS Q-branch spectrum that is the most perturbed of the four SO₃ isotopomers we have studied. The relative importance of these interaction terms on the ν₁ CARS spectrum is examined in some detail and accurate rovibrational constants are determined for all of the mixed states, leading to deperturbed values of 1004.662(24), 0.0003503(9), and 0.0007066(12) cm⁻¹ for ν₁, α₁^B, and α₁^C, respectively. The B_e value is found to be 0.310875(12) cm⁻¹, which gives an equilibrium bond length r_e of 141.7339(3) pm, in excellent agreement with values of 141.7340(1) and 141.7347(7) pm reported earlier for ³²S¹⁶O₃ and ³⁴S¹⁶O₃.     

Analysis of the ν3 and ν1 infrared bands of GeH4

The high-resolution infrared spectrum of GeH₄ in the region 2020 to 2200 cm^?1 was analyzed. Most of the observed lines were assigned to transitions of the ν₃ and ν₁ bands of the five naturally occurring isotopic species. The spectrum was fitted by diagonalizing the v₃ = 1 and v₁ = 1 Hamiltonians coupled by the dominant vibration-rotation interaction term. For each isotopic species, about 100 transitions were fitted with an overall standard deviation of 0.006 cm^?1, using only 10 adjustable parameters. The five sets of parameters obtained are consistent with the expected isotope effects.     

The infrared spectra of SiH3F: ν3 and ν4 bands

Infrared spectra of silyl fluoride were recorded at a resolution of 0.06 cm^?1 using a Nicolet Fourier transform interferometer. Analyses of the ν₃ and ν₄ bands are presented for ²⁸SiH₃F, together with work on ²⁹SiH₃F, ³⁰SiH₃F, and various hot bands.     

Analysis of the ν2 and ν4 infrared bands of CD4

The infrared spectrum of totally deuterated methane CD₄ has been recorded between 930 cm^?1 and 1180 cm^?1 under high resolution (0.003 cm^?1). The ν₂ and ν₄ bands of ¹²CD₄ have been reanalyzed on the basis of a complete third-order Hamiltonian including all the coupling terms linking the upper states of the two bands. A set of only 16 self-consistent parameters have been adjusted to fit more than 1650 assigned transitions reaching a maximum upper state J value of 20. The obtained standard deviation is 0.0041 cm^?1. In addition, 171 lines of the ν₄ band of ¹³CD₄ have been assigned. They have been analyzed, in the same dyad scheme, by adjusting 7 parameters of the ν₄ band together with the main ζ₂₄ Coriolis parameter. The obtained standard deviation is only 0.0012 cm^?1.     

Splitting of the near infrared absorption bands of Sm in POCl3:SnCl4, POCl3:ZrCl4 and POCl3:TiCl4

The near infrared absorption spectra of Sm³⁺ in POCl₃:SnCl₄, POCl₃:ZrCl₄ and POCl₃:TiCl₄ consist of a series of bands, attributed to the ⁶H_5/2 → ⁶F_J transitions. Each one of these absorption bands is split into three components. The extent of splitting differs slightly from state to state. For each component of the ⁶F-multiplet the splitting decreases gradually from POCl₃:SnCl₄ to POCl₃:ZrCl₄ and POCl₃:TiCl₄. Energy differences between adjacent components of the near infrared absorption bands vary from a maximum of 166 cm⁻¹ to a minimum of 123 cm⁻¹. The band half-widths of the corresponding components vary from 86 to 120 cm⁻¹. At lower temperatures the intensity of the high energy component increases whereas the intensity of the entire absorption band envelope, associated with each component of the ⁶F-multiplet, remains almost constant. The splitting observed is attributed to the Stark splitting of the ⁶H_5/2-state of Sm³⁺ into three components, in conjunction with appropriate Stark splitting of the states of the ⁶F-multiplet.     

Absorption properties of the near infrared CO2 bands

The equivalent widths of the near i.r. CO₂ bands at 1.4, 1.6, 2.0, 2.7, 4.8 and 5.2 μm have been measured for various sample parameters. By comparing the data obtained for pure CO₂ samples with theoretical values resulting from line0by-line calculations, band intensities have been determined for these six bands. The data obtained for the mixtures of CO₂ with N₂ have been used to check the validity of the band intensities thus determined. These data have also been used to check the applicability of the empirical formulae proposed by Howard, Burch and Williams.     

An anharmonic force field for SO3

An anharmonic force field for SO₃ based on the valence force model has been investigated. The results of extending the model to include some further estimated cubic interaction potential constants have also been investigated. The phenomenological parameters calculated from both model force fields agree with those few values which have been experimentally determined. A calculation of the inertia defect has been made, and thus the value of C₀ has been determined. The equilibrium structure has been determined to be: $\text{r}{}_{\mathrm{e}}\text{= 1.4184 ± 0.0010}\text{A}\text{?}$.     

The infrared spectra of HCF3 and DCF3

Experimental measurements of the infrared spectra of HCF₃ and DCF₃ are reported with emphasis on the overtone and combination bands and on the numerous resonances which occur. These include Fermi, l-type, and Coriolis x-y resonances.     

The infrared bands ν2 and ν5 of CH3Br with Coriolis interaction

The infrared bands ν₂ and ν₅ of CH₃Br have been measured at a resolution of 0.015 cm^?1. The lines due to the isotopic species CH₃⁷⁹Br and CH₃⁸¹Br were resolved and altogether about 3000 lines were assigned. The bands were analyzed simultaneously by taking into account the xy-Coriolis resonance between the states v₂ = 1 and v₅ = 1. A local perturbation observed in ν₅ could be explained in terms of a (1,?2) resonance between v₂ = 1 and v₅ = 1. Some perturbation allowed transitions could be assigned and they give an equation between A₀ and D₀^K.     

The 3ν3 overtone bands of UF6 and UF6

The absorption specta of CO laser radiation by 3ν₃ overtone bands of ²³⁸UF₆ and ²³⁵UF₆ has been measured using photoacoustic spectroscopic techniques. For the two temperatures 250 K and 290 K, measured absorption coefficients and cross-sections of the 3ν₃ band of ²³⁵UF₆ are reported for the first time.     

The high-resolution infrared spectra of the ν2 and ν3 bands of HOCl

The infrared spectra of the a-type transitions of the ν₂ and ν₃ bands of HO³⁵Cl and HO³⁷Cl have been obtained under high resolution. Line assignments of both bands have been made, and the spectroscopic constants have been obtained for both bands using a Watson Hamiltonian. Lines of the K_a = 5 subband of the ν₂ band of the HO³⁵Cl molecule were found to be slightly shifted by an interaction with the K_a = 4 level of the 2ν₃ vibrational state. The b-type transitions permitted for both bands were too weak to observe. Relative intensities of selected lines of both bands have been measured, and empirical Herman-Wallis factors have been determined.     

Some Raman bands of C3O2

The ν₁, ν₅, 2ν₅, and 2ν₆ Raman band accumulations of carbon suboxide, C₃O₂, have been photographed with a resolution of 0.2–0.3 cm^?1. Each band accumulation consists, in addition to the main band, of a large number of “hot” bands due to the extremely low, highly anharmonic ν₇ fundamental vibration. In the 2ν₆ band accumulation a few series of unresolved Q branches have been assigned. In the ν₁ and 2ν₅ band accumulations most Q branches almost coincide, forming a very intense peak, whereas the dominating feature of the ν₅ band accumulation is a minimum, in agreement with the expectation of an extremely weak Q branch for a Π_g fundamental band. Tentative values of ν₁ = 2196.9 ± 0.1 cm^?1 and ν₅ = 580.2 ± 0.5 cm^?1 as well as several energy values in the ν₇ manifold of the 2ν₆⁰ state are obtained. Further, improved exposures of the ν₂ + 2ν₇⁰ band accumulation yield some levels in the ν₇ manifold of the ν₂ state, in addition to those determined previously.     

EPR evidence of local lattice mode in K3H(SO4)2 and Rb3H(SO4)2 fast-proton conductors

The observation of an anomalous temperature dependence of Mn²⁺ EPR spectra linewidth and nonaxial crystal-field parameter in K₃H(SO₄)₂ and Rb₃H(SO₄)₂ allows one to suggest the presence of “local mode” predicted by Yamada (Ferroelectrics 170 (1995) 23). The activation energy for this kind of excitation was found and equals 11.3 (0.5) and 7.4 (0.3) meV for Mn²⁺ doped K₃H(SO₄)₂ and Rb₃H(SO₄)₂, respectively.     

High-resolution infrared and microwave spectroscopy of the ν4 and 2ν2 bands of 14NH3 and 15NH3

More than two thousand Stark resonances of the ν₄ and 2ν₂ band transitions of ¹⁴NH₃ and ¹⁵NH₃ were observed at Doppler-limited resolution with a CO laser. Fourier transform infrared spectroscopy on ¹⁵NH₃ is also carried out. Thirty-six new microwave transitions including seven perturbation-enhanced transitions are observed in the v₄ = 1 excited vibrational state of ¹⁴NH₃ and ¹⁵NH₃. Accuracies of all available spectroscopic data on the v₄ = 1 and the v₂ = 2 states are evaluated and analyses of the vibration-rotation spectra are performed. The Coriolis interaction between the closely lying v₄ = 1 a (antisymmetric level) and v₂ = 2 s (symmetric level) states is explicitly included in the analysis. Smaller Coriolis interactions between the v₄ = 1 a and the v₂ = 1 s states and between the v₂ = 2 s and the v₂ = v₄ = 1 a states (i.e., (v₁, v₂, v′₃, v′₄) = (0 1 0⁰ 1¹)) are also taken into consideration. The accuracy in determination of the principal molecular constants is 10^?6. The parameters thus obtained reproduce the frequencies of the vibration-rotation transitions and inversion transitions within the accuracy of 0.0024 cm^?1.     

The infrared spectrum of the ν1 and ν4 bands of 28SiH3D

The spectrum of the ν₁ and ν₄ SiH stretching bands of ²⁸SiH₃D have been recorded and analyzed. The degenerate stretching mode is at 2188.504 cm^?1, only 1.103 cm^?1 above the symmetric stretching mode. Several accidental and essential resonances affect these bands but all have been successfully analyzed by diagnolization of the secular determinant complete through the second order of the transformed Hamiltonian. One accidental resonance leads to a number of forbidden transitions through which a value of the rotational constant A₀ has been obtained.     

High-resolution infrared spectrum of the ν3 and ν2 + ν3 − ν2 bands of 14N16O2

The infrared absorption spectrum of the ν₃ band of ¹⁴NO₂ has been recorded with a resolution and a frequency accuracy much improved over the previous investigations. The K- and N-line assignments have been greatly extended and a more accurate set of spectroscopic constants derived. Several lines in the subbands with K_a ≥ 3 have been observed to be doubled by spin-rotation interaction and spin-rotation interaction constants have been obtained. Several weak series of lines in the spectrum (K_a = 0, 1, 2, and 3) have been unambiguously assigned to the “hot band” ν₂ + ν₃ ? ν₂. Lines of the K_a = 3, 4, 5, and 6 sub-bands of ν₃ have been found to be perturbed by a Coriolis interaction with the K_a = 4, 5, 6, and 7 levels of 2ν₂.     

Zero field splittings of Gd3+IN Nd2(SO4)3 · 8H2O and Sm2(SO4)3 · 8H2O crystals at 273 K

The electron paramagnetic resonance (EPR) of Nd₂(SO₄)₃ · 8H₂O and Sm₂(SO₄)₃ · 8H₂O doped with Gd³⁺ has been carried out at 273 K and the spin-Hamiltonian parameters are deduced. The zero field splittings have been computed and compared with those observed directly by Bogle and Symmons. It is found that the discrepancy in the zero field splittings. between computed and directly observed values falls within the range of linewidths of directly observed values.     

EPR studies of Gd3+-doped Ce2(SO4)3.8H2O and La2(SO4)3.9H2O single crystals

EPR spectra of Gd³⁺-doped Ce₂(SO₄)₃.8H₂O and La₂(SO₄)₃.9H₂O single crystals have been measured with an X-band spectrometer at room and low temperatures. The absolute signs of spin Hamiltonian parameters have been determined for the La₂(SO₄)₃.9H₂O host from intensities of lines at liquid helium temperature; for the Ce₂(SO₄).8H₂O host the lines broaden considerably below 60 K, not permitting the determination of absolute signs of spin Hamiltonian parameters. The data are analysed using a rigourous least-squares procedure, fitting simultaneously all lines obtained for several orientations of the external magnetic field. The zero-field splittings have been computed for both the hosts. The characteristics of EPR spectra of Gd³⁺ in these hosts are compared with those obtained in other rare-earth trisulphate octahydrate hosts.     

The assignment of ν2 and ν4 of SO3

Three experiments have been performed to resolve an uncertainty in the assignment of ν₂ and ν₄ for SO₃: (i) the gas phase Raman spectrum has been measured; (ii) the infrared active combination band ν₃ + ν₄ has been measured; (iii) a band contour calculation has been performed taking account of the ?-type resonance in ν₄ and a strong Coriolis resonance between ν₂ and ν₄. These experiments establish beyond any doubt that ν₂ lies at about 497.5 cm^?1 and ν₄ lies at about 530.2 cm^?1. The contour calculation also shows that the Coriolis resonance gives rise to a positive intensity perturbation.