Mobilities of H+3 and HeH+ ions in helium gas and rate coefficient for HeH+ + H2 → H+3 + He

The mobilities of mass-identified H⁺₃ and HeH⁺ ions in helium and the reaction rate coefficient for HeH⁺ + H₂ → H⁺₃ + He have been measured by a drift-tube quadrupole mass spectrometer at 300 K. The zero-field reduced mobilities of H⁺₃ and HeH⁺ ions, corrected to 273 K, are 31.0 ± 0.8 and 23.4 ± 0.6 cm² V^?1 s^?1 respectively. The reaction rate coefficient was found to be (1.26 + 0.16) × 10^?9 cm³s^?1 and was observed to be independent of the mean ion kinetic energy in the range from 0.04 to 0.3 eV.     

Vibration intervals for tritiated H+3 and D+3

Ab initio calculated values of fundamental vibrational frequencies and zero-point energies are presented for HTD⁺, D₂T⁺, T₂D⁺, H₂T⁺, T₂H⁺ and T⁺₃.     

Laser induced photodissociation of H+2 and D+2 ions

Photodissociation of H⁺₂ and D⁺₂ has been observed in a crossed beam experiment. A laser used as photon source. The ion and laser beam cross each other inside the laser cavity. The momentum spectra of the resulting H⁺ or D⁺ fragments are recorded with a mass spectrometer. From the spectra the excess kinetic energy is calculated. These values agree with the theoretically expected ones within the experimental error. From the measured intensity distribution the relative population for several vibrational states in the primary ion beam is calculated. Our values deviate from the usual assumed Franck-Condon pattern as well as from the values reported by Dunn. The angular dependence of the fragments is also measured. This dependence indicates a polarization of the primary beam perpendicular to its direction.     

Solution raman spectra and normal coordinate analysis of the H3CPH+3 and H3CPD+3 cations

The Raman spectra of solutions of H₃ CPH₃⁺ and H₃ CPD₃⁺ in aqueous concentrated hydrochloric and deuterochloric acid are reported together with polarisation data. A complete vibrational assignment is given on the basis of C_3v, symmetry except for the inactive A₂ mode. A set of valence force constants and potential energy distributions have been calculated from the data of the two isotopes H₃ CPH₃ and H₃⁺ CPD⁺₃. For H₃ CPD⁺₃ the potential energy distribution demonstrates strong interaction between the P-C stretching and the symmetrical PD₃ deformation mode.     

Low energy crossed beam study of the endothermic charge transfer reaction H+2(Ar,H2)Ar+

A crossed beam study of the title reaction if reported, from 0.45 to 7.8 eV. The reaction is predominantly translationally endothermic. At the lowest energy, there is evidence for two reaction paths: a long-range electron transfer and an intimate collision with electron transfer. Branching ratios for the competitive proton transfer reaction are presented.     

An improved James function for the ground state of H+2

The James function for the ground state of H⁺₂ has been corrected through first order of Rayleigh–Schrödinger perturbation theory. The resulting energies are effectively exact over a range of internuclear separations from 0 to 5 au.     

Rotation energies for deuterated H+3 oscillators in zero-point states of vibration

Previous ab initio studies of deuterated H⁺₃ molecular ions are extended to include rotational modes for the zero-point states of vibration. Rotation energies are obtained using direct numerical diagonalization of vibration—rotation hamiltonian matrices, and nuclear wavefunctions as superpositions of mode-coupled anharmonic rotationless vibrators and related prolate symmetric top eigenfunctions. Relevance to recent searches for interstellar H₂D⁺ is noted.     

Vibrational effects in proton and charge transfer in the H+2 + Ar system

Reaction and charge transfer of H⁺₂ + Ar to give ArH⁺ and Ar⁺ have been investigated as a function of H⁺₂ vibrational quantum state and kinetic energy (Ec.m.), using photoionization and guided beam ion optics. Resonance effects are important in charge transfer; proton and charge transfer are closely coupled for Ec.m. 3 eV.     

Reactions of O+4 and O+2 with methane

Rate coefficients and products were determined for the title reactions employing a drift tube mass spectrometer apparatus. The implications of these reactions for the ion chemistry of the stratosphere is discussed.     

Photodissociation of the dimer ions Ar+2, Ne+2, and (CO2)+2

The tandem quadrupole photodissociation mass spectrometer has been used to study photodissociation reactions of Ar⁺₂, Ne⁺₂, and (CO₂)⁺₂. The cross sections for photodissociation of Ar⁺₂ exhibited a strong dependence on ion source pressure, varying from 2 × 10 ^?18cm² at 0.1 torr to 6 × 10^?19cm² at 0.5 torr. A large photodissociation cross section (2 × 10^?17cm² for the reaction (CO₂)⁺₂ → CO⁺₂+ CO₂ was observed at the red end of the visible spectrum (580–620 nm) suggesting that this may be an important reaction in CO₂ rich planetary ionspheres such as that of Mars.     

Test of projected perturbation theory on a simplified model of H+2

The perturbation theory for projected states is shown to converge for a schematic one-dimensional model of H⁺₂. Ordinary perturbation theory diverges for the odd state. It converges for the even state, but very marginally for large interactive distance.     

Electronic nonadiabatic transitions in the reactive (Ar+ + H2, Ar + H+2, ArH+ + H) system. Numerical results for the collinear configuration

In this communication are presented exact quantum mechanical nonadiabatic electronic transition probabilities for the collinear reaction Ar⁺ + H₂(v_i = 0) → ArH⁺(v_f) + H. The calculations were performed using a potential surface calculated by the DIM method. It is established that large probabilities (≈ 1.0) can be obtained only if there is enough translational energy to overcome a potential barrier formed due to the crossing between v_i = 0 of the Ar⁺ + H₂ system and v_i = 2 of the Ar + H⁺₂ system. The threshold for the reaction is found to be 0.06 eV.     

Ci calculations of the low lying electronic states of the radical SiH3, SiH+3 and SiH−3

SCF and CI calculations for the silicon-hydrogen compounds SiH₃, SiH⁺₃ and SiH^? with D_3h and C_3v geometries are carried out f     

A kinetic study of proton transfer reactions of NH+4, CH3NH+3, and PH+4 with calcium atoms

Cross section measurements for the proton transfer reactions of NH⁺₄, CH₃NH⁺₃, and PH⁺₄ with Ca(g) have been obtained over a range of low ion kinetic energies. For all reactions studied the cross sections drop sharply with increase in ion kinetic energy, indicating exothermic behavior. The results show that Ca(g) is an unusually strong base with a proton affinity in excess of 9.2 eV. Cross sections for the PH⁺₄Ca reaction are an order to magnitude higher than those for the NH⁺₄Ca reaction for ion energies between one and three eV. This effect is not explained by simple theories of ion-induced dipole interactions. It is suggested that the enhanced rate of the PH⁺₄Ca reaction may be due to d-orbital participation.     

Quantum mechanical treatment of the collinear H+ + H2 system. The uncoupled system

A fully converged close coupling study is performed of the collinear (H⁺ + H₂) system on the lower potential energy surface. The surface is derived by the DIMZO (diatomic in molecules-zero overlap) method. Transition probabilities for the reactions: H⁺ + H₂ (ν = 0, 1) → H₂ (ν′) + H⁺; ν′ = 0,..., 7 are given for a number of total energies in the range from 1 eV to 3 eV. It is found that for this energy region the transition ν = 0 → ν′ = 0 is the most preferential. This fact leads us to believe that addition of the upper surface will have a minor effect on the calculated probabilities of transitions from ν = 0 in the above-mentioned energy range.     

AB initio calculations of the stability of the OH+4 and FH+3 ions

Some geometric configurations of the OH⁺₄ and FH⁺₃ ions have been calculated by the SCF MO LCAO method using linear combinations of gaussian lobe functions. The total electronic energies of the systems under study are lower than the sum of the energies for H₂O and H⁺₂ or OH⁺₃ and H, and HF and H⁺₂ or FH⁺₂ and H, respectively.     

The laser sensitized reaction SF26 + NO + O3

A pulsed CO₂ laser was used to irradiate a rapidly flowing mixture of NO, O₃, and SF₆. When the laser was tuned to an SF₆ absorption line, an increase in the visible NO^*₂ emission was observed. The laser-induced signal has two unusual features. First, the rise time is much longer than is observed when O₃ is excited directly, and, second, the signal decays to a value above the original baseline. The rise rate is attributed to VV energy transfer from SF²₆ to O₃, while the baseline shift is attributed to a temperature jump resulting from rapid non-resonant VV relaxation within the SF₆ molecule. Both the size of the T-jump and the fraction of vibrationally excited ozone molecules vary inversely with NO pressure.     

The SO+2 radical-ion

From the complex overall EPR spectrum of ⁶⁰Co gamma-irradiated pure solid sulfur dioxide the spectrum of the SO⁺₂ radical-ion was selected and the following principal values for the g-tensor obtained: g₁ = 1.9620;g₂ = 2.0026;g₃ = 2.0118 (Δg = ± 0.0005).     

Phase diagram for the system KVO3 + NH4HCO3 + NH4VO3 + KHCO3 + H2O at 303 K

Solubility data of the KVO₃ + NH₄HCO₃ + NH₄VO₃ + KHCO₃ + H₂O system at 303 K were determined under varying pressure conditions. The results were used to construct a phase diagram in the oblique projection according to Jänecke's method. At constant p and T this diagram includes two invariant points, five double saturated liquid curves, and four crystallization fields corresponding to KVO₃, NH₄HCO₃, NH₄VO₃, and KHCO₃. It has been found that ammonium meta-vanadate is a sparingly soluble salt. NH₄VO₃ and KHCO₃ compose the stable pair of salts, whereas KVO₃ and NH₄HCO₃ form the unstable salt-pair. A thorough knowledge of the solubility phase diagram for this reciprocal quaternary salt system is the theoretical basis of the carbonation process of the potassium meta-vanadate saturated ammonia solution.