Rate coefficient for the reaction OH + HO2 = H2O + O2 at 1 atmosphere pressure and 308 K

The rate coefficient for the reaction OH + HO₂ =H₂O + O₂ has been determined from measurements of the steady-state absorption of HO₂ at 210 nm, in low-frequency square-wave modulated photolysis of O₃ + H₂O mixtures. The value obtained was (9.9 ± 2.5) × 10^?11 cm³ molecule^?1 s^?1 at 308 K and 1 atm pressure.     

Laser excited fluorescence of I2

The fluorescence spectrum of iodine was investigated from 200 to 520 nm in the presence and absence of buffer gases following excitation of I₂ with 193 nm photons. The pressure dependence of the fluorescence and tentative transition assignments for one new and several less well-known I₂ emission bands are discussed.     

A crossed molecular beam study of the chemiluminescent reaction Xe(3P2,0) + BrCN → Xe(1S0) + Br + CN(B2Σ+)

The chemiluminescent interaction of Xe(³P_2,0) and BrCN has been studied under crosscd-beam conditions at collision energies ranging up to 70 kj mol^?1. The CN(B → X) fluorescence spectrum, the excitation function for its production and the fluorescence polarisation - or rather its absence - have been determined. The results can be explained by a two-stage harpooning mechanism involving an inert-gas cyanide (Xe⁺CN^?)¹ intermediate but not by a “sensitisation” mechanism proceeding through electronic energy transfer.     

Detection of the ππ* E2g state in sym-tetrafluorobenzene

The VUV absorption spectrum of gaseous 2,3,5,6-tetrafluorobenzene is reported up to its first IP. The absolute extinction coefficient and f value are given. A band appearing at 6.85 eV is attributed to the E_2g benzene parent state with f = 0.06. A similar band is found in 1,3,5-trifluorobenzene, where the E_2g ← A_1g transition is symmetry allowed.     

Laser-induced photodissociation of He+2

The momentum distributions of He⁺ fragments from photodissociation of He⁺₂ ions have been recorded in a crossed-beams experiment. The discrete values of the kinetic energy releases can be predicted from the vibrational spacings in the ground state of the primary ions.     

Production of the n2 herman infrared system by the energy pooling reaction of N2(Δ3Σ+u) metastable nitrogen molecules

Molecular N₂ emission, observed from an Ar(³Po, 2) and Xe(³P₂) + N₂ flowing afterglow apparatus, indicates that the energy pooling reaction by 2N₂(A ³Σ⁺_u) generates the emission from the Herman infrared system, which is an unassigned nitrogen band system. A lower limit to the formation rate constant for the upper state of the Herman infrared system was found to be 2.5 × 10^-11 cm³ molecule^?1 s^?1. The information presented here may help in the identification of the upper and lower states of the emission system. The 2N₂(A) energy pooling reaction also forms N₂(B³ Π_g, v? 8) but a rate constant cannot be assigned from the present data.     

NMR study of hydrogen molybdenum bronzes: H1.71MoO3 and H0.36MoO3

Proton NMR relaxation times (T₂T₁, and T_1?) and absorption spectra are reported for the compounds H_1.71MoO₃ (red monoclinic) and H_0.36MoO₃ (blue orthorhombic) in the temperature range 77 K < T < 450 K. Rigid lattice dipolar spectra show that both compounds contain proton pairs, as OH₂ groups coordinated to Mo atoms in H_1.71MoO₃ and as pairs of OH groups in H_0.36MoO₃. The room temperature lineshape for H_1.71MoO₃ shows that the average chemical shielding tensor has a total anisotropy of 20.1 ppm. The relaxation measurements confirm that hydrogen diffusion occurs and give E_A = 22 kJ mole^?1 and $\text{τ}{}^0{}_{\mathrm{<mtext>C</mtext>}}\text{? 10}{}^{\mathrm{?13}}\text{sec}$ for H_1.71MoO₃ and E_A = 11 kJ mole^?1 and $\text{τ}{}^0{}_{\mathrm{<mtext>C</mtext>}}\text{? 3 × 10}{}^{\mathrm{?8}}\text{sec}$ for H_0.36MoO₃.     

Rotationally resolved photoelectron angular distributions for H+2(ν′ = 0) at λ = 584 and 736 Å

The photoelectron asymmetry parameter for H⁺₂(ν′ = 0) was measured for the S rotational branch at λ = 584 and 736 Å using supersonic beam of n-H₂. Comparison with the theoretical β values of Itikawa demonstrates the importance of coupling between the p and f photoelectron waves at higher photon energy.     

New experimental evidence for the energy corrected sudden scaling law

New measurements of rate constants for the rotationally inelastic process Na₂^*(j_o) + Xe → Na₂^*(j_f) + Xe show the superiority of the energy corrected sudden scaling law of DePristo and Rabitz over other such laws, including the statistical power gap law which we proposed earlier, particularly at high j_o. All rates decrease as an inverse power of the energy transfer.     

Pulsed NMR study of NH4+ β-alumina

Proton NMR relaxation times T₂, T₁, and T_1? are reported for NH₄⁺ β-alumina powder in the temperature range 77 K < T < 500 K at 16 MHz. The measurements show that the NH₄⁺ ions both reorient and translate. The translational process can be characterized by the parameters E = 20 kJ mole^?1 and τ⁰_d = 3 × 10^?11 sec. Relaxation at high temperatures is dominated by dipolar coupling to paramagnetic impurities. Reasons for the different activation energies measured using NMR and other techniques for β-alumina compounds are discussed.     

Franck-condon factors for I2 lines arising from Ar, K and He-Ne laser excitation

We report Franck-Condon factors for the I₂ B → X transitions excited by several lines of Ar⁺, Kr⁺ and He-Ne lasers and observed in fluorescence. The most recent and accurate molecular constants of Luc have been used in the calculation.     

Laser-induced fluorescence measurement of the nascent rotational distribution of N+2 (X2Σ+g) formed by electron impact on N2

The internal state distribution of ground state N⁺₂ ions formed from N₂ by electron impact ionization is measured under collision-free conditions using laser-induced fluorescence. Analysis of the B–X (0, 0) band shows the rotational distribution to be characterized by a temperature which increases slightly with decreasing electron energy (60–100 eV). Cascade contributions are unimportant.     

Laser induced fluorescence in NO2: absolute fluorescence cross sections and quantum yields

Spectrally resolved collision-free absolute fluorescence cross sections have been measured, for NO₂ excited, by the second harmonic of the Nd: YAG laser. The total cross section into the 523.0–650.0 nm range was found to be 2.3 × 10^?20 cm². The measured absorption cross section of 1.46 × 10^?19 cm² implies a quantum yield of 16% over this range.     

Theoretical study of structure and stability of h+x (h2)n clusters

The ion clusters H⁺X· (H₂)_n (X = N₂, CO, O₂ and H₂ andn = 0, 1, 2) are investigated by means of SCF and CI computations in a double-zeta plus polarization gaussian basis It is found that hydrogen molecules attack the proton of H⁺X perpendicularly. The calculated stabilization energies are in agreement with experimental values of δH⁰.     

The forbidden raman (v2, πu) transition in crystalline CS2

Raman spectra associated with the v₂(π_u) bending vibration of CS₂, which is forbidden for an isolated molecule, are presented The spectra are assigned to combination bands with phonons and show well-resolved critical point structure.     

Symmetry adapted versus symmetry broken wavefunctions: the 1s core level ions of O+2

It is shown that, for O₂, in a MC SCF determination of the core ionization potentials employing the full Molecular point group, very few (N-1)-particle configurations are required in order to account for the symmetry breaking in the corresponding Hartree-Fock calculations.     

The molecular structure of selenonyl fluoride,SeO2F2, and sulfuryl fluoride,SO2F2, as determined by gas-phase electron diffraction

The molecular structure of selenonyl fluoride (SeO₂F₂) and sulfuryl fluoride (SO₂F₂) has been studied by gas-phase electron diffraction. The geometries of both molecules are consistent with predictions of VSEPR (valence-shell electron-pair repulsion) theory. The results for the more important distance (r_a), bond angle, and r.m.s. amplitude (l) parameters with estimated uncertainties estimated at 2σ are for SeO₂F₂r(Se = 0) = 1.575 Å (0.002), r(Se-F) = 1.685 Å (0.002), ∠OSeO = 126.2° (0.5), ∠FSeF = 94.1° (0.5), l(Se = 0) = 0.0440 Å (0.0046), l(Se-F) = 0.0472 Å (0.0042), and for SO₂F₂r(S = 0) = 1.397 Å (0.002), r(S-F) = 1.530 Å (0.002), ∠OSO = 122.6° (1.2), ∠FSF = 96.7° (1.1), l(S = 0) = 0.0331 Å (0.0015), l(S-F) = 0.0393 Å (0.0018).     

Reactions of water with carbon and ethylene over illuminated pt/tio2

The room temperature reaction between gas phase water and active carbon to form carbon dioxide and hydrogen on a platinized titanium dioxide catalyst, illuminated with band gap radiation, is reported. Using the same catalyst system, ethylene is converted to ethane, carbon dioxide, hydrogen and a small amount of methane.     

Esr studies on the reactive character of the radical anions,so−2, so−3 and so−4 in aqueous solution

The reactive characteristics of the oxy anion radicals of sulphur, SO^?₂, SO^?₃ and SO^?₄ were investigated by use of the rapid-mixing flow technique coupled with electron spin resonance (ESR) which can detect the radicals having a lifetime of 5–100 msec. The SO^?₂ reduced the aromatic nitro compounds to the corresponding anion radicals, but did not abstract the hydrogen from the saturated compounds nor add to the unsaturated compounds. The SO^?₃ could add to the compounds having CC bond, but did not abstract the hydrogen from the saturated compounds nor reduce the aromatic nitro compounds. The SO^?₄ could abstract the hydrogen from the saturated compounds and also add to the unsaturated compounds having CC bond, but did not reduce the aromatic nitro compounds. These differences of the reactivity towards the organic substrates were discussed on the basis of the difference in the distribution of the unpaired electron density of each radical anion.     

Calorimetric and spectroscopic studies of the critical phase transition in (CH3NH3)2[SnCl6]

(CH₃NH₃)₂[SnCl₆] undergoes a critical phase transition at 154.32 ± 0.06 K with the critical exponents α = 0.36 ± 0.04, α' = 0.19 ± 0.02, the critical entropy ratio 0.062 and the total transition entropy (1.60 ± 0.18) R. Infrared spectral change favors the order-disorder mechanism of the transition proposed from the thermodynamic data.