Investigation of the kinetics of OH∗ and CH∗ chemiluminescence in hydrocarbon oxidation behind reflected shock waves

The temporal variation of chemiluminescence emission from OH^?(A² Σ ⁺) and CH^?(A² Δ) in reacting Ar-diluted H₂/O₂/CH₄, C₂H₂/O₂ and C₂H₂/N₂O mixtures was studied in a shock tube for a wide temperature range at atmospheric pressures and various equivalence ratios. Time-resolved emission measurements were used to evaluate the relative importance of different reaction pathways. The main formation channel for OH^? in hydrocarbon combustion was studied with CH₄ as benchmark fuel. Three reaction pathways leading to CH^? were studied with C₂H₂ as fuel. Based on well-validated ground-state chemistry models from literature, sub-mechanisms for OH^? and CH^? were developed. For the main OH^?-forming reaction CH+O₂=OH^?+CO, a rate coefficient of k ₂=(8.0±2.6)×10¹⁰ cm³?mol^?1?s^?1 was determined. For CH^? formation, best agreement was achieved when incorporating reactions C₂+OH=CH^?+CO (k ₅=2.0×10¹⁴ cm³?mol^?1?s^?1) and C₂H+O=CH^?+CO (k ₆=3.6×10¹²exp(?10.9 kJ?mol^?1/RT) cm³?mol^?1?s^?1) and neglecting the C₂H+O₂=CH^?+CO₂ reaction.     

A−2 production in π−p interactions at 3.9 GeV/c

The reaction π^?p → A^?₂p at 3.9 GeV/c incident momentum is studied using data corresponding to the ?^°π^?, ηπ^? and K^δ_sK^? decay modes of the A^?₂. Unnatural parity exchange is found to be important at this energy. The natural parity exchange component of the differential cross section exhibits structure at t′ ≈ GeV².     

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.     

Production of pion and muon pairs in e±e− colliding beams. Extension of the equivalent photon approximation

The reactions e^?e^?→e^?e^?π⁺π^?(μ⁺μ^?) are considered here in the situation where only pions (muons) are recorded and k_⊥ (total transverse momentum of the pair) is not too small (roughly speaking m_e²?k_⊥²?m_π²); this domain gives the main contribution to the cross section. In this paper the differential cross sections have been obtained to an accuracy of (Ink_⊥²/me²)^?1k_⊥/m_π. The amplitudes with one scalar photon have to be taken into account in this approximation. Also the charge asymmetry appears due to the interference of the two-photon and bremsstrahlung diagrams. It is shown what information on amplitudes of the reaction γγ→π⁺π^? and on the pion electromagnetic form factor can be obtained from an experiment in the given set-up.     

Two-photon annihilation into pion pair

The first experimental study of the interaction γγ → π⁺π^t- has been carried out in the region of ?(660) through the reaction e⁺e^? → e⁺e^?π⁺π^?. Based on two observed events, the γγ width of ?(660) is obtained to be Γ_?γγ = 9.6_?8.0^+12.3 keV. Applied on this, theory of P.C.D.C. anomaly predicts R_∞ = 5.8_?3.5^+3.2 for the asymptotic value of σ(e⁺e^? → hadrons)/σ(e⁺e^? → μ⁺μ^?).     

Intervalley magnetophonon resonance peak of thermoelectric power in the phonon drag region of p-Te

A large peak is found at 3.2 Tesla (T) in the second derivative curve of longitudinal magneto-Seebeck coefficient (-?²α₆/?H² of p-type tellurium below 20 K under the magnetic field H6c. The peak height is rapidly increasing with decreasing temperature, in contrast to disappearance of the usual oscillation due to LO phonon which is observed between 20 and 100 K. A small peak is also appreciable in the second derivative of longitudinal magnetoresistance (-?²?₆/?H² at the same field of 3.2 T. The peaks both in -?²α₆/?H² and -?²?₆/?H² are interpreted as a resonance peak due to the intervalley scattering by longitudinal acoustic (LA) phonon between the two valleys split off by inversion asymmetry splitting (μ_BGH). This interpretation gives a value of G as 5.5 in good agreement with the value of G = 5 ± 1 determined by the Shubnikov-de Haas experiment. It is explained by t he phonon drag effect based on this interpretation that the peak of -?²α₆/?H² is much more prominent than that of -?²?₆/?H² and increases with decreasing temperature.     

Structural phase transition and octahedral tilting in the calcium titanate perovskite CaTiO3

Crystal structure of the calcium titanate perovskite CaTiO₃ was refined by the Rietveld analysis of neutron diffraction data collected over the temperature range of 296 to 1720 K. The orthorhombic Pbnm-tetragonal I4/mcm phase transformation reversibly occurred at 1512 ± 13 K and the tetragonal I4/mcm-cubic Pm3?m transition was reversibly observed at 1635 ± 2 K. The structural phase transitions are characterized by the tilt of the TiO₆ octahedron. The tilt systems of the Pbnm, I4/mcm, and Pm3?m CaTiO₃ are ?_x^??_y^??_z⁺ (?_x^? = ?_y^?), ?_x⁰?_y⁰?_z^?, and ?_x⁰?_y⁰?_z⁰, respectively. Here the ?_x^?, ?_z⁺, and ?_x⁰ stand for the out-of-phase tilt angle of TiO₆ octahedron along x axis, the in-phase octahedral tilt angle along z axis, and no octahedral tilting along x axis, respectively. All the tilt angles, ?_x^?, ?_z⁺, and ?_z^? decreased with increasing temperature where the critical exponents were about 0.25. The ?_x^? and ?_y^? of the orthorhombic structure decreased discontinuously to ?_z^? of the tetragonal structure or 0° through the Pbnm-I4/mcm transition. The tilt angle, the unit-cell parameters and unit-cell volume discontinuously changed at the Pbnm-I4/mcm transition temperature, indicating the first-order nature. The increase of the cell volume in the Pbnm-I4/mcm transition was 0.088 vol.%. In contrast, the unit-cell volume continuously increased and the tilt angle ?_z^? continuously decreased with increasing temperature and became 0° at the I4/mcm-Pm3?m transition temperature, indicating a continuous nature of the transformation. The Pbnm-I4/mcm and I4/mcm-Pm3?m phase transitions are induced by the tilting of TiO₆ octahedra, indicating the displacive nature of the transitions. The larger thermal motion of O2 atom in I4/mcm CaTiO₃ indicates the larger positional disorder of O2 atom, which is consistent with the tilt system ?_x⁰?_y⁰?_z^?.     

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.     

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.     

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.     

Determination of the radiative widths of the η′ and A2 from two-photon exchange production

From the two-photon exchange processes e⁺e^? → e⁺e^?η' (958) → e⁺e^??⁰γ and e⁺e^? → e⁺e^?A₂ (1310) → e⁺e^?π⁺π^?π⁰ observed using the CELLO detector at PETRA the radiative widths of the η' and A₂ have been determined with the results: Γ_γγ(η') = 5.4 ± 1.0[stat.] ± 0.7[syst.] keV; Γ_γγ(A₂) = 0.59 ± 0.14[stat.] _?0.08^+0.31[syst.] keV.     

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.     

Isospin and density waves in asymmetric nuclear matter

The excitation of small density oscillations (zero sound) and isospin oscillations (isospin sound) in cold asymmetric nuclear matter (in the ground state ?⁰_n> ?⁰_p, ?⁰ = ?⁰_n+?⁰_p = 0.17 nucleons/fm³) is investigated within the framework of the Landau theory of normal Fermi liquids. There is only one undamped mode of excitation, which consists predominantly of isospin oscillations, with some admixture of density oscillations. The phase velocity of this undamped wave depends very weakly on the neutron excess and is close to that of a pure isospin wave (isospin sound) in symmetric nuclear matter of the same density. At the neutron excess corresponding to that existing in heavy nuclei the amplitude of the density oscillations constitutes about 30 % of the amplitude of the neutron excess density oscillations. Calculation with a suitably parametrized charge dependent quasiparticle interaction in asymmetric nuclear matter shows that for (?⁰_n??⁰_p)/?⁰ > 0.63 both zero sound and isospin sound are strongly damped.     

Carrier concentration dependence and temperature dependence of mobility in silicon (100) N-channel inversion layers at low temperatures

The carrier concentration (N_s) dependence of electron mobility in Si (100) inversion layers has been measured at temperatures T = 1.5?70K for high- and low-mobility MOSFETs. An extrinsic term is observed in the T-dependent part of the scattering probability, τ^?1_T. At T = 4.4 K, τ^?1_T depends on N_s as N^?1.9_s in low mobility samples. In high-mobility samples, τ^?1_T increases with increasing N_s in high N_s region while τ^?1_T ∝ N^?1.6_s in low N_s region. The N_s-dependence of τ^?1_T becomes weaker with increasing T in both of low- and high-mobility samples. At N_s = 3 × 10¹² cm^?2, τ^?1_T depends on T as T^1.8 in low-mobility samples and τ^?1_T ∝ T^2.0 in high- mobility samples at T 5 K.     

A high-resolution study of the 14.4-μm infrared band of deuterofluoroform

The FT-IR spectrum of the ν₃ parallel band of deuterofluoroform has been recorded at a resolution of 0.0045 cm^?1. Nine independent spectral parameters were determined which reproduce some 650 observed wavenumbers with a standard error of 3 × 10^?4 cm^?1. The constants derived for the ν₃ band are (in cm^?1): ν₀ = 694.2822(3); B₀ = 0.3309321(9); B₃ = 0.3302464(11); α^B = 6.859(10) × 10^?4; α^C = 1.429 × 10^?4; D₃^J = 3.168(3) × 10^?7; D₀^J = 3.188(3) × 10^?7; D_JK³ = 4.766 × 10^?7; D_JK⁰ = 4.864 × 10^?7; and D_K⁰ ? D_K³ = 2 × 10^?10.     

The 2880-Å emission spectrum of I2: Ion-pair states near 47 000 cm−1

An emission system of I₂ in Ar in the region 2830–2890 Å is examined under high resolution and found to display fine violet-degraded band structure. This system is interpreted as a charge-transfer transition originating from an ion-pair state near 47 000 cm^?1 and terminating on a weakly bound state which dissociates to two ground-state atoms. This interpretation is supported by spectral simulations employing a bound-free model. The transition is tentatively assigned as $\text{0}{}_{\mathrm{<mtext>g</mtext>}}{}^{\mathrm{?}}\text{→ 2431 0}{}_{\mathrm{<mtext>u</mtext>}}{}^{\mathrm{?}}\text{(}{}^3\text{Π}\text{)}$, according to which the excited state becomes the fourth ion-pair state near 47 000 cm^?1 to be experimentally characterized, and the lower state is the last component of the lowest ³Π state to be identified. The vibrational assignments include about 45 bands in ¹²⁷I₂ and ¹²⁹I₂, spanning v′ = 0–4 and v″ = 6–19, but with the numbering of the lower state remaining uncertain by several units. The main spectroscopic constants for the excited state are T_e = 47 070 cm^?1, ?_e = 105.7 cm^?1, ?_ex_e = 0.49 cm^?1. The spectral simulations place the lower state's potential curve 34 650 cm^?1 below the upper state at R = R′_e, with slope ?850 cm^?1/Å. For our “best” numbering of the lower state, ?_e = 20.5 cm^?1, ?_ex_e = 0.29 cm^?1, T_e = 12 190 cm^?1, and D_e = 360 cm^?1.     

Magnetic monopoles in neutron stars

The effects of monopole-antimonopole annihilation on a previously reported bound [1] on the product of the galactic flux of grand unified magnetic monopoles and the cross section for monopole catalyzed nucleon decay: (F_M/cm^?2s^?1sr^?1)(σ_ΔB/10^?2 cm²) ? 10^?22 are examined for several models of neutron star interiors. For neutron stars with superconducting interiors or large internal magnetic fields this bound is unaltered. In the unlikely event that old neutron stars are not superconducting and have internal magnetic fields B_int ? 10⁸ Gauss the effects of monopole-antimonopole annihilation relax the bound to (F_M/cm^?2 s^?1 sr^?1)(σ_ΔB/10^?27 cm^?2)² ? 10^?18. Magnetic monopoles may also have a significant effect on the structure of the interior magnetic field in neutron stars.     

Far-infrared rotational spectra of some freons; chlorotrifluoromethane,dichlorodifluoromethane, and trichlorofluoromethane

The far-infrared rotational spectra of chlorotrifluoromethane, dichlorodifluoromethane, and trichlorofluoromethane have been observed with an interferometric (Fourier transform) spectrometer in the region 10–40 cm^?1 at a resolution of 0.07 cm^?1. CCl₂F₂ exhibits a continuum spectrum at this resolution, but symmetric top rotational fine structure is observed for CClF₃ and CCl₃F. Isotope splitting is also observed in CClF₃, and analysis yields the rotational constants for C³⁵ClF₃ of B₀ = 0.11112 cm^?1, D_J = 1.6 × 10^?8cm^?1; and for C³⁷ClF₃, B₀ = 0.10835 cm^?1, D_J = 1.5 · 10^?8cm^?1. Isotopic shifts can be allowed for in CCl₃F to yield constants for C³⁵Cl₃F of B₀ = 0.0821 cm^?1, D_J = 1 × 10^?8cm^?1. These values are all in agreement with those deduced from microwave studies of the low J transitions apart from B₀ for C³⁵ClF₃, where the difference is outside the expected experimental error.     

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.     

Tau decays into kaons

Predictions for semi-leptonic decay rates of theτ lepton into two meson final statesK ^?π⁰ v _τ, $\overline {K^0 } \pi - v_\tau $ ,K ⁰ K ^? v _τ, and three meson final statesK ^?π^? K ⁺ v _τ, $K^0 \pi ^ - \overline {K^0 } v_\tau $ ,K _sπ^? K _s v _τ,K _sπ^? K _L v _τ,K _Lπ^? K _L v _τ,K ^?π⁰ K ⁰ v _τ, π⁰π⁰ K ^? v _τ,K ^?π^?π⁺ v _τ, π^? K ⁰π⁰ v _τ are derived. The hadronic matrix elements are expressed in terms of form factors, which can be predicted by chiral Lagrangians supplemented by informations about all possible low-lying resonances in the different channels. Isospin symmetry relations among the different final states are carefully taken into account. The calculated branching ratios are compared with measured decay rates where data are available.