Coherent Raman and Infrared Studies of Sulfur Trioxide

High-resolution (0.001 cm⁻¹) coherent anti-Stokes Raman scattering (CARS) was used to observe the Q-branch structure of the IR-inactive ν₁ symmetric stretching mode of ³²S¹⁶O₃ and its various ¹⁸O isotopomers. The ν₁ spectrum of ³²S¹⁶O₃ reveals two intense Q-branches in the region 1065–1067 cm⁻¹, with surprisingly complex vibrational–rotational structure not resolved in earlier studies. Efforts to simulate this with a simple Fermi-resonance model involving ν₁ and 2ν₄ states do not reproduce the spectral detail, nor do they yield reasonable spectroscopic parameters. A more subtle combination of Fermi resonance and indirect Coriolis interactions with nearby states, 2ν₄(1=0, ±2), ν₂+ν₄(1=±1), 2ν₂(1=0), is suspected and a determination of the location of these coupled states by high-resolution infrared measurements is under way. At medium resolution (0.125 cm⁻¹), the infrared spectra reveal Q-branch features from which approximate band origins are estimated for the ν₂, ν₃, and ν₄ fundamental modes of ³²S¹⁸O₃, ³²S¹⁸O₂¹⁶O, and ³²S¹⁸O¹⁶O₂. These and literature data for ³²S¹⁶O₃ are used to calculate force constants for SO₃ and a comparison is made with similar values for SO₂ and SO. The frequencies and force constants are in excellent agreement with those obtained by Martin in a recent ab initio calculation.     

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.     

The submillimeter wave spectrum of 32S16O2, 32S16O2(ν2), and 34S16O2

Extensive new measurements in the region 400–1000 GHz have been made on ³²S¹⁶O₂, ³²S¹⁶O₂(ν₂), and ³⁴S¹⁶O₂. These measurements represent almost a threefold extension in the frequency region for which high-resolution microwave data are available. These data have been combined with the previously available microwave data for this analysis. The results, when extrapolated into the far infrared, compare favorably with recent results obtained from high-resolution FIR spectroscopy.     

High-resolution measurements of the ν2 and 2ν2-ν2 bands of SO2

Infrared measurements have been made on SO₂ between 450 and 602 cm⁻¹ with a resolution of 0.005 cm⁻¹. The B-type bands due to the bending mode transitions 010-000 and 020-010 have been assigned and analyzed for the ³²S¹⁶O₂ molecule. A total of 3007 transitions were measured and fit for ³²S¹⁶O₂ with a standard deviation of 0.0004 cm⁻¹. Ro-vibrational constants are given that fit the current measurements and the pure rotational transitions reported in the literature.     

Spectral intensities in the ν1 band of carbonyl sulfide and its isotopic species

A tunable diode laser was used to perform measurements of absolute lines intensities in the ν₁ fundamental of carbonyl sulfide. Spectra have also been recorded for the following isotopic species: ¹⁶O¹²C³⁴S, ¹⁶O¹³C³²S and ¹⁶O¹²C³³S. The vibrational band strength S_v⁰ was calculated at 298 K. The absolute intensity for 100% of ¹⁶O¹²C³²S species is found to be S_v⁰ = 29.69 ± 0.15 cm⁻² atm⁻¹ with the uncertainty covering three times the standard deviation. We have tried to determine the α-coefficient involved in the Hermann-Wallis factor F = (1 + αm + )² and the value is found to be negligible (−5 ± 8) × 10⁻⁵. The S_v⁰ value obtained for the other isotopic species is very close to the normal one.     

Linewidth and intensity measurements of SO2 lines at 94 GHz with self-broadening and broadening by H2O and N2

In the frequency range between 91.5 and 95.5 GHz, three rotational lines of the ³²S¹⁶O₂ and two rotational lines of the ³⁴S¹⁶O₂ molecules in the fundamental vibrational state, and also two lines of the ³²S¹⁶O₂ molecule in the v₂ vibrational state, have been investigated. Center frequencies and absolute absorptions have been measured and compared with theoretical values. Furthermore, the self-broadening and broadening by H₂O and N₂ of the transition 23(6,18)–24(5,19) with the line center at 94.064 GHz have been investigated. The following linewidth parameters were found: SO₂-SO₂, 18.2±0.3 MHz/torr; SO₂-N₂, 3.8±0.1 MHz/torr; SO₂-H₂O, 15.2±0.2 MHz/torr. The bridge spectrometer and the measuring method used are also described.     

Observation of oriented 23 S 1 helium atoms in a sodium-helium plasma irradiated by polarization-modulated laser radiation

An experiment on the observation of spin polarization of metastable helium atoms interacting with optically oriented sodium atoms under continuous rf discharge conditions is described. Laser radiation with alternating-sign circular polarization, tuned to the resonance excitation of the 3² S _1/2–3² P _1/2 transition in Na atoms, is used as the source for optical pumping of ground-state sodium atoms. Pis’ma Zh. éksp. Teor. Fiz. 65, No. 5, 385–387 (10 March 1997)     

NO dissociation and N2 production in the presence of co-adsorbed SO2 and D2 on Pt(3 3 2)

NO dissociation and subsequent N₂ production in the presence of co-adsorbed S¹⁸O₂ and D₂ on the surface of stepped Pt(3 3 2) were studied using Fourier transform infra red reflection–absorption spectroscopy (FTIR-RAS) combined with thermal desorption spectroscopy (TDS). Reduction of NO by D (D₂ is adsorbed dissociatively on Pt surfaces) proceeds to a limited extent, because this reaction is rate-controlled by NO dissociation and the supply of D atoms at the higher surface temperatures at which NO dissociation becomes significant (350 K and higher). NO–D reaction is suppressed in the presence of S¹⁸O₂, depending significantly on the S¹⁸O₂ coverage and the competition between the reactions NO–D and S¹⁸O₂–D. When the supply of D₂ is limited, e.g., 0.1 L in this study, the presence of S¹⁸O₂ suppresses the NO–D reaction. With a sufficient supply of D₂, e.g., 0.4 L and higher, D-atom competing reactions do not play a role any more because the reactions of both NO and S¹⁸O₂ with D proceed only to a very limited extent. As such, generation of O atoms from S¹⁸O₂ dissociation is the main reaction that leads to the suppression in NO dissociation and consequently, N₂ production.It is also concluded that the presence of S¹⁸O₂ does not seriously poison the active sites on the Pt surface, providing that there is a sufficient D supply to remove O atoms from both NO dissociation and S¹⁸O₂ dissociation.     

Diode laser heterodyne spectroscopy on the ν1 band of sulfur dioxide

Diode laser heterodyne techniques have been used to obtain the frequencies of 55 ir absorption lines of ³²S¹⁶O₂. From these data and from previous microwave and millimeter wave measurements, new spectroscopic constants for the ν₁ band have been determined. The new constants have been used to predict new optically pumped submillimeter wave emissions.     

Formation and quenching mechanisms of excited particles in an oxygen-iodine laser medium

New values of a number of kinetic constants of processes proceeding in oxygen-iodine laser media are presented. The total probabilities of formation of I₂(X, 15 ≤ v ≤ 24) and I₂(X, 25 ≤ v ≤ 47) molecules in the course of quenching of I* atoms by I₂(X) are found to be 0.9 and 0.1, respectively. The quantum yield of singlet oxygen in the reaction O(¹ D) + N₂O → N₂ + O₂(a ¹Δ) is close to 100%. The quenching rate constants of I₂(A’) by O₂, H₂O, CO₂, I₂, and Ar and of I(² P _1/2) by O(³ P), O₃, NO₂, N₂O₄, and N₂O are presented.     

Breakdown of the reduction of the rovibrational Hamiltonian: The case of SO2F2

The ground state rotational spectrum of the near-spherical top molecule S¹⁸O₂F₂ (sulfuryl fluoride) has been measured from 50 to 700 GHz. As for the parent isotopologue, S¹⁶O₂F₂ [K. Sarka, J. Demaison, L. Margulès, I. Merke, N. Heineking, H. Bürger, H. Ruland, J. Mol. Spectrosc. 200 (2000) 55-64], it was necessary to use a non-reduced Hamiltonian in order to obtain a satisfactory fit. It was possible to determine six quartic centrifugal distortion constants (instead of five for a standard asymmetric top) and five sextic constants (one of them not existing in the reduced Hamiltonian) could also be determined. This ground state level has also been analysed thanks to a tensorial formalism developed in Dijon. Only two tensorial sextic constants are fixed to zero, all others have been adjusted. Although S¹⁸O₂F₂ is less spherical than S¹⁶O₂F₂, the analysis was more difficult. It is partly due to the fact that S¹⁸O₂F₂ is oblate whereas S¹⁶O₂F₂ is prolate. The experimental quartic centrifugal distortion constants were found in good agreement with those calculated from the force field, confirming the correctness of the analysis.     

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.     

Self-interstitial configuration in molybdenum studied by modified analytical embedded atom method

The stability of various atomic configurations containing a self-interstitial atom (SIA) in a model representing Mo has been investigated using the modified analytical embedded atom method (MAEAM). The lattice relaxations are treated with the molecular dynamics (MD) simulation at absolute zero of temperature. Six relatively stable self-interstitial configurations and formation energies have been described and calculated. The results indicate that the [111] dumbbell interstitial S₁₁₁ has the lowest formation energy, and in ascending order, the sequence of the configurations is predicted to be S₁₁₁, C, S₁₁₀, T, S₀₀₁ and O. From relaxed displacement field up to the fifth-NN atoms of six configurations, we know that the relaxed displacements depend not only on separation distances of the NN atoms from the defect centre but also strongly on the direction of the connected line between the NN atoms and the defect centre. The equilibrium distances between two nearest atoms in the core of the S₁₁₁, C, S₁₁₀, T, S₀₀₁ and O configurations are 0.72a, 0.72a, 0.71a, 0.72a, 0.70a and 0.70a, respectively.      

Neutron scattering study of short-range correlations and ionic diffusion in copper selenide

The paper reports the results of a neutron scattering study of Cu_{2 - d}Se {\hbox{C}}{{\hbox{u}}_{{2 - \delta }}}{\hbox{Se}} superionic compounds. The crystallographic model fitted to the diffraction data shows the occupation of 8c and 32f sites by Cu atoms. Observed diffuse background is related to correlated thermal vibrations of Se and Cu atoms, with Se↔Cu (8c,32f) and Cu (8c)↔Cu (8c) correlations being most important. The quasi-elastic neutron experiments show the decrease of the self-diffusion coefficient with the deviation from the stoichiometry due to the longer residence time of Cu ions between diffusion hops. Combination of neutron diffraction, diffuse scattering and quasi-elastic scattering experimental data suggests that the Cu atoms diffuse between the nearest 8c sites through the 32f sites.     

Experimental Study and Modelling of Formation and Decay of Active Species in an Oxygen Discharge

A microwave (2.45 GHz) oxygen discharge (3 hPa, 150 W, 50 mL.min^–1) is studied by optical emission spectroscopy of O(⁵P) (line 777.4 nm) and of the atmospheric system of O₂(head‐line 759.4 nm). Calibration of the spectral response of the optical setup is used to determine the concentrations of O(⁵P) and O₂(b). The concentration of the O(⁵P) atoms is in the range 108–109 cm^–3 and the concentration of the O₂(b) molecules is in the range 10¹⁴ – 2 × 10¹⁴ cm^–3 along the discharge tube. An attempt is made to simulate the experimental results by using coupling the Boltzmann equation, homogeneous energy transfer V‐V and V‐T, heterogeneous reactions on the walls (energy transfer and recombination of atoms) and a kinetic scheme (electronic transfer and chemical reactions). The Boltzmann equation includes momentum transfer, inelastic and superelastic processes and e‐e collisions. V‐V and V‐T transfer equations are obtained from the SSH theory and the kinetic scheme includes 65 reactions with 17 species [electrons e, ions O^– and O₂^–, fundamental electronic neutral species O(³P), O₂, O₂(X,v), O₃ and excited neutral species O₂(a), O₂(b), O₂(A), O(¹D), O(¹S), O(⁵P), O(4d ⁵D^o), O(5s ⁵S^o), O(3d ⁵D^o) and O(4s ⁵S^o)]. A fair agreement between experimental results and modelling is obtained with the following set of fitting values: – heterogeneous deactivation coefficient for O₂(b) γ = 2.6 × 10^–2; – rate constant of reaction [O(¹D) + O(³P) → 2 O(³P)] k₃₄ = 1.4 × 10^–11 cm³.s^–1; – electron concentration in the range 10¹⁰ – 10¹¹ cm^–3. Modelling shows that the recombination coefficient for oxygen atoms on the silica wall (range 1.4 × 10^–3 – 0.2 × 10^–3) is of the same order as the values obtained in a previous paper and that the ratio ([O] / 2 [O₂]initial) is about 33–50%. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

ESR and Chemical Bonding of Some Copper Complexes

ESR spectra of copper (II) was measured in 33 copper complexes which were synthesized in this laboratory and the bonding parameter α²of copper was calculated according to the method proposed by Kivelson. ⁽¹⁾ The results of these calculations are classified, together with the data quoted from the literature,^1-5into four groups according to the kinds of ligand atoms, i.e., α²is 0.72 to 0.87 for 0₄ - type complexes, 0.69 to 0.86 in N₂O₂, 0.74 to 0.82 in N₄, and 0.54 to 0.62 in S₄ and S₂₃N₂ type complexes, where 0, H and S refer the oxygen, nitrogen and sulfur atoms of ligands, respectively, that directly coordinate with copper.     

Spectroscopic and laser properties of Er3+-doped monoclinic BaY2F8 single crystals

The luminescence and absorption properties of Ba(Y_1−x Er _x )₂F₈ (x=0.001, 0.01, 0.05, 0.1, 0.2 and 0.3) and the Er³⁺-ion decay kinetics of luminescent transitions from three initial laser states, the⁴S_3/2,⁴F._9/2 and⁴I_11/2 manifolds, were measured. The crystal-field splitting schemes for allJ-manifolds which are involved in (J →J′)-luminescence transitions and stimulated emission parameters of Er³⁺ -ions in BaY₂F₈ were determined. A comparison of laser powers and efficiencies of BaY₂F₈ and Y₃Al₅O₁₂, Lu₃Al₅O₁₂ and LiYF₄ single crystals doped with Er³⁺-ions shows the similar performance of these materials.

     

Characterization of laser-induced plasma plume: Comparison between Al and Al2O3 targets

Characterization of the plasma plume produced by laser ablation from Al and Al₂O₃ targets was carried out on the basis of the line profile analysis of Al(I) (²P°–²S) emission. The spatial distribution and density parameters of electrons and Al atoms in the plume were obtained by comparing observed spectral line profiles with a theoretical calculation. The results showed different behavior for the Al and Al₂O₃ targets. The Al atoms from the Al₂O₃ target were populated in a smaller region than those from the Al target. PACS 52.38.MF; 52.70.Kz; 52.25.Os     

Far-infrared laser emission from deuterated ammonia

By optically pumping the deuterated isotopomers of ¹⁴NH₃ and ¹⁵NH₃ using ¹²C¹⁶O₂, ¹³C¹⁶O₂, ¹²C¹⁸O₂, and ¹³C¹⁸O₂ lasers, several new far-infrared (FIR) emission lines between 65 μm and 125 μm have been detected. The existing spectroscopy of ¹⁴N-ammonia isotopomers has been used to identify many of these lines, as well as some previously observed but unidentified. The spectroscopic data have been analyzed to predict over 20 additional FIR laser lines that could be pumped by a more capable CO₂ laser. This effort was motivated by a need for strong laser lines in frequency coincidence with molecular transitions of astrophysical interest. Of particularnote is the measurement of the 2680-GHz line of ¹⁴NHD₂, whose frequency is 4.9 GHz higher than that of the important J=1-0 line of interstellar HD. Received: 25 July 2002 / Published online: 20 December 2002 RID="*" ID="*"Corresponding author. Fax: +1-303/492-5941, E-mail: boreiko@spot.colorado.edu     

Compact variational wave functions for bound states in three-electron atomic systems

The variational procedure to construct compact and accurate wave functions for three-electron atoms and ions is developed. The procedure is based on the use of six-dimensional Gaussoids written in the relative four-body coordinates r ₁₂, r ₁₃, r ₂₃, r ₁₄, r ₂₄, and r ₃₄. The nonlinear parameters in each basis function have been carefully optimized. Using these variational wave functions, we have determined the energies and other bound state properties for the ground 1² S-states in a number of three-electron atoms and ions. The three-electron atomic systems considered in this work include the neutral Li atom and nine positively charged lithiumlike ions: Be⁺, B²⁺, C³⁺, ..., Na⁸⁺, and Mg⁹⁺. Our variational wave functions are used to determine the hyperfine structure splitting and field shifts for some lithium-like ions. The explicit formulas of the Q ⁻¹ expansion are derived for the total energies of these three-electron systems. The article is published in the original.