- H3++O: An experimental study
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We have measured the reaction rate coefficient and branching ratios for the H3++O atom reaction using a flowing afterglow/selected ion flow tube operating at room temperature (295±5 K). The measured rate coefficient was k=(1.2±0.5)×10-9 cm3 s-1 and the branching ratios were OH++H2, (70%) and H2O++H (30%). This reaction has some relevance to the synthesis of water in interstellar clouds.
- Milligan, Daniel B.,McEwan, Murray J.
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p. 482 - 485
(2008/10/08)
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- The A 2A1-X 2B1 transition of H2O+ in the near infrared region
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A titanium sapphire laser spectrometer along with velocity modulation detection was used to record, between 12 000 and 13 400 cm-1, the absorption spectrum of the A 2A1-X 2B1 electronic transition of H2O+ produced in an ac glow discharge with a gas mixture of He/H2O. The Σ(0,7,0)-(0,0,0) transition has been observed at 13 411 cm-1 and revised rotational assignments are presented. The Δ(0,7,0)-(0,0,0) and Π(0,6,0)-(0,0,0) transitions have been observed for the first time, at 13 331 and 12 494 cm-1, respectively. The vibrational assignment follows the vibrational numbering of Brommer et al. [J. Chem. Phys. 98, 5222 (1993)]. The rotational analysis was performed using the combination differences technique. Strong perturbations are observed, they are tentatively explained in term of rovibronic interactions. A set of effective molecular parameters has been obtained for each vibrational level of the A state. The values of the spin-orbit parameter are reported, they illustrate the vibronic coupling between the two electronic states.
- Huet,Hadj Bachir,Destombes,Vervloet
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p. 5645 - 5651
(2007/10/03)
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- Observation of the visible absorption spectrum of H2O+
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The A2A1-X2B1 system of H2O+ has been observed, using laser absorption spectroscopy in a velocity-modulated discharge.A total of 78 transitions between 14 794 and 15 475 cm-1 have been observed with an uncertainty (1 SD) of 0.02 cm-1, including 76 transitions in the (0,7,0)-(0,0,0) band and 2 in the (0,8,0)-(0,0,0) band.This species is important for cometary astronomy, and intriguing for molecular physics because of its prominent Renner-Teller interaction.Careful measurements were made of the relative intensities of the absorption lines, which were measured to an accuracy of 13percent (1 SD).This is the first observation of the >A-X transition in absorption; all previous data were obtained in emission with conventional grating spectroscopy.The transition frequencies of our new data are in good agreement with previous work, and have improved accuracy.The new data have definite rejection of the interfering lines from excited neutral H2 that plagues previous work.Compared with previous work, the new data have the first quantitative measurement of intensities.The ratio of the Franck-Condon factors I8/I7 = 0.99 +/- 0.43 has been measured for the first time, where Iv = FCF.
- Das, Biman,Farley, John W.
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p. 8809 - 8815
(2007/10/02)
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- Cross section and product time-of-flight measurements of the reaction of N2+ with H2O and D2O at suprathermal energies
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Charge exchange and hydrogen atom pickup cross sections, and product ion time-of-flight measurements are reported for N2+-H2O(D2O) collisions at center-of-mass collision energies ranging between 1 and 15 eV.No isotope effect is detected for the
- Dressler, Rainer A.,Gardner, James A.,Salter, Richard H.,Wodarczyk, Francis J.,Murad, Edmond
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p. 1117 - 1125
(2007/10/02)
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- Ion-Molecule Reactions Involving H3O+, H2O+, and OH+ at Thermal Energy
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The rate coefficients for a variety of reactions involving OH+, H2O+, and H3O+ with CS2, H2S, SO2, NO, NO2, N2O, N2, O2, CH4, CO2, CO, NH3, and H2 are obtained with a selected ion flow tube.The product channels include proton transfer, charge transfer, atom abstraction, and association.Most of the reaction rates are fast and have high reaction efficiencies.Reaction of OH+ with NO2 is found to produce both NO2+ and NO+; even though both reaction channels are also exothermic with H2O+, only NO2+ is produced.H3O+ is found to undergo association reactions with SO2 and N2O and H2O+ does so with CO2 and N2O.The reaction of H2O+ with N2O also involves a second-order process in addition to the association pathway.
- Shul, R. J.,Passarella, R.,DiFazio, L. T.,Keesee, R. G.,Castleman, A. W.
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p. 4947 - 4951
(2007/10/02)
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- Pressure and temperature dependences of the binary ion-molecule reaction N3+ + H2O-->H2NO+ + N2
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Experiments were carried out using a time-resolved atmospheric pressure ionization mass- spectrometer (TRAPI) in N2-H2O (1 ppm) system at temperatures from 233 to 543 K and at pressures from 167 to 760 Torr.The title reaction showed temperature and pressure dependences which were explained by the following scheme: N3+ + H2O(N3+*H2O)* (forward and backward rate constants ka and kb; (N3+*H2O)*-->H2NO+ + N2 (forward rate constant kp; (N3+*H2O)* + N2-->H2NO+ + 2N2 (forward rate constant kd).Assuming that kd is equal to the collision rate constant of 7.1*10-10 cm3 s-1, the individual rate constants were determined as ka = 2.8*10-9 cm3 s-1 (302 K), kb = 17T3.6 s-1 where Tis temperature in K, and kp = 2.0*109 s-1 ( 302 K) .The product H2NO+ ion changed by successive reactions with H2O into H2NO+*H2O and subsequently to H3O+.
- Matsuoka, Shingo,Nakamura, Hirone
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p. 5663 - 5669
(2007/10/02)
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- The yield of oxygen and hydrogen atoms through dissociative recombination of H2O+ ions with electrons
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The branching ratios of the dissociative recombination of excited H2O+ ions with electrons were studied using a plasma flow tube experiment.The total oxygen atom channel accounts for 45percent of the recombination with more than 24percent in O + H + H .The remaining channel is OH + H for 55percent.These results are discussed in comparison with the few available theories and with photodissociation data.
- Rowe, B. R.,Vallee, F.,Queffelec, J. L.,Gomet, J. C.,Morlais, M.
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p. 845 - 850
(2007/10/02)
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- Thermal Energy Charge-Transfer Reactions of Ar+ and Ar2+
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The rate coefficients for a number of thermal energy charge-transfer reactions are obtained with a recently completed selected ion flow tube (SIFT).The ion-molecule reactions studied involve Ar+ and Ar2+ with a variety of neutral molecules including O2, CS2, CO2, SO2, H2O, H2S, NH3, NO, SF6, CH4, N2O, and CO.The relative magnitudes of the observed rate coefficients are not in accord with an energy resonance model which requires favorable Frank-Condon factors.Furthermore, we find that the dimer ion reaction rate constant is not always greater than that of the monomer with a special neutral although there is greater phase space in the case of the dimer where the dissociative channel leads to a three-body final state.However, the proximity of the recombination energy of Ar+ and Ar2+ to a band in the photoelectron spectra of the neutral appear to explain the relative rates of the monomer and the dimer reactions with a specific neutral.
- Shul, R. J.,Upschulte, B. L.,Passarella, R.,Keesee, R. G.,Castleman, A. W.
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p. 2556 - 2562
(2007/10/02)
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- Crossed Molecular Beam Studies of Proton Transfer, Unimolecular Decay, and Isotope Scrambling in the Reactions H2+ + H2O, H2+ + D2O, and D2+ + H2O
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We present and experimental study of the title reactions over the collision energy range from 0.7 to 6.9 eV.Over the entire collision energy range, a significant fraction of the products have internal excitation sufficiently high to undergo unimolecular decay to H2O+ or an isotopically substituted water cation.An examination of the reactions D2+ + H2O and H2+ + D2O and observation of H2O+ and HOD+ products of unimolecular decay at 3.0 and 6.3 eV suggest that, at the lower collision energy, the recoil energy distributions are consistent with the results of phase space calculations including all vibrations of the H2O+ or HOD+ product.At this collision energy, the unimolecular decay products have barycentric angular distributions with sharp forward-backward symmetry, suggesting that planar scattering with concomitant angular momentum polarization is an important dynamical feature in these reactions.At the higher collision energy, the complex 'osculates' with a lifetime too short for rapid intramolecular energy transfer.We also present evidence for a direct reaction between H2+ and D2O yielding HOD+ and a bound HD molecule, proceeding through a four-center exchange reaction rather than through unimolecular decay of HD2O+.
- Bilotta, R. M.,Farrar, J. M.
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p. 1515 - 1526
(2007/10/02)
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