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  • Electronic Resource  (37)
  • 1990-1994  (37)
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  • Electronic Resource  (37)
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  • 1
    Electronic Resource
    Electronic Resource
    The formation and destruction of H3O− (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 5706-5714 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report the first measurements of rate constants for formation and reaction of the hydrated-hydride ion H3O−. We studied the Kleingeld–Nibbering reaction [Int. J. Mass Spectrom. Ion Phys. 49, 311 (1983)], namely, dehydrogenation of formaldehyde by hydroxide to form hydrated-hydride ion and carbon monoxide. The OD−+H2CO reaction is about 35% efficient at 298 K, with OD−/OH− exchange occurring in about half the reactions. H3O− was observed to undergo thermal dissociation in a helium carrier gas at room temperature with a rate constant of 1.6×10−12 cm3 s−1. We also studied a new reaction in which H3O− is formed: The association of OH− with H2 in a He carrier gas at low temperatures. The rate coefficient for this ternary reaction is 1×10−30 cm6 s−1 at 88 K. Rate coefficients and product branching fractions were determined for H3O− reactions with 19 neutral species at low temperatures (88–194 K) in an H2 carrier. The results of ion-beam studies, negative-ion photoelectron spectroscopy, and ion-molecule reaction data allow us to specify the hydride–water bond energy D0298(H−−H2O)=14.4±1.0 kcal mol−1 (0.62±0.04 eV). The heat of formation of H3O−, −37.5±1.0 kcal mol−1, and the proton affinity of H3O−, 386.0±1.0 kcal mol−1, are derived from these results. Dissociation of H3O− into OH− and H2 requires 4.5±1.0 kcal mol−1 energy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467136
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  • 2
    Electronic Resource
    Electronic Resource
    Negative ion reactions with PF5 and the electron affinity of PF5 (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 7200-7205 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Rate coefficients and product branching fractions have been determined for 31 ion–molecule reactions involving PF5 or PF−5. About half of the reactions studied show an ion–molecule association channel. NH−2 and OH− reaction with PF5 yields HF product. F− and electron transfer channels are also observed in many of the reactions studied. Consideration of the efficiency of the electron transfer channel in these reactions leads to the conclusion that the adiabatic electron affinity of PF5 is 0.75±0.15 eV.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466918
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  • 3
    Electronic Resource
    Electronic Resource
    Thermal decomposition of H3O− produced in reaction of OH− with H2CO (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 357-361 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The ion–molecule reaction OH−+H2CO→H3O−+CO has been studied at 300 K with isotopic labeling of reactants. The H3O− product is only observed in small abundance because the ion dissociates into OH−+H2 upon multiple collisions in a helium buffer gas. Without isotopic labeling, the pseudo-first-order kinetics plots for the reactions of OH− with H2CO and OD−+D2CO were found to be curved as a result of the regeneration of OH− or OD− reactant. A scavenger technique was used to remove the H3O− (or D3O−) produced prior to dissociation, to reveal the true first-order attenuation of OH− (or OD−) in reaction with H2CO (or D2CO). The rate constant for the OH−+H2CO reaction is 7.6×10−10 cm3 s−1, and for OD−+D2CO is 5.7×10−10 cm3 s−1. For the isotopically mixed cases OH−+D2CO and OD−+H2CO, the rate constants are equal to 1.3×10−9 cm3 s−1, about twice as large as those for the reactions involving only a single hydrogen isotope, indicating that isotopic exchange is an important process. The rate constants for the thermal dissociation of H3O− and D3O− in helium were found to be 1.6×10−12 and 1.1×10−12 cm3 s−1, respectively, within a factor of 2. The results are discussed in terms of other thermal dissociation reactions of ions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466949
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  • 4
    Electronic Resource
    Electronic Resource
    Electron detachment reactions of fluorinated carbanions with atomic hydrogen (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 1767-1768 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Rate constants were measured for electron detachment reactions of atomic hydrogen with CF−3, C2F−5, and C3F−3. The experiments were performed using a selected ion flow tube (SIFT) instrument. The density of atomic hydrogen was calibrated by studying the reaction of F− with H, and rate constants were measured relative to the known rate constant for this reaction. The reactions with H are fast, proceeding at 17%–66% of the collisional rates. No ionic products were observed for any of the reactions studied. While associative detachment is exothermic for all three anions, other reactive detachment processes are also possible. These anions were found to be unreactive with H2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466605
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  • 5
    Electronic Resource
    Electronic Resource
    A reexamination of the vibrational–vibrational energy transfer from N2(v) to NO+ (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 6579-6582 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have reexamined whether N2(v=1) transfers its vibrational quantum to NO+(v=0). In light of recent results that show that CH3I does not charge transfer rapidly with NO+(v=1), we show that previous measurements could not have detected vibrational–vibrational (V–V) energy transfer from N2(v=1) to NO+(v=0). We have made measurements to examine this process by using C2H5I as the monitor for NO+(v=1). Our results show that NO+(v(approximately-greater-than)0) is indeed produced from reaction of NO+(v=0) with N2(v) but these results cannot be used to distinguish between resonant V–V energy transfer from N2(v=1) to NO+(v=0) and V–V, T energy transfer from higher levels of N2(v).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465849
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  • 6
    Electronic Resource
    Electronic Resource
    Erratum: The photodissociation spectrum of SO2+ [J. Chem. Phys. 84, 1215 (1986)] (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 3582-3582 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465113
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  • 7
    Electronic Resource
    Electronic Resource
    Reactions of Ar+ with halocarbons and of I+ with CF3I (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 173-179 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The gas phase reactions of Ar+ with the halocarbons CF3Cl, CF3Br, CF3I, CF4, C2F6, and C2F4 have been studied using a variable temperature-selected ion flow tube (VT-SIFT) instrument operated at 298 and 500 K. Rate constants and product branching percentages were measured at both temperatures. Ar+ reacts at the collisional rate with all of the above neutrals at both 298 and 500 K. The reactions with CF3X yield CF+3 and CF2X+ for all X (the reaction with CF4 produces only CF+3 ). For X=I, there is an additional channel leading to the ionic product I+. The reaction of Ar+ with C2F6 produces both CF+3 and C2F+5. The reaction of Ar+ with C2F4 forms a rich product spectrum consisting of the ions CF+, CF+2, CF+3, C2F+3, and C2F+4. The reaction product distributions are compared with results from ionization experiments such as photoion–photoelectron coincidence (PIPECO) and electron impact mass spectrometry, and in some cases excellent agreement is found. The reaction of I+ with CF3I, which is a secondary reaction in the Ar+/CF3I system, was investigated at 298 K in separate experiments. This reaction is rapid and forms four product ions: CF+3, CF2I+, CF3I+, and I+2. The results are compared with previously published information.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.463605
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  • 8
    Electronic Resource
    Electronic Resource
    Rotational temperature dependence of the branching ratio for the reaction of O+ with HD (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 8120-8123 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Rate constants and branching fractions for the reaction of O+ with HD have been measured as a function of average center-of-mass kinetic energy (〈KEcm〉) at three temperatures: 93, 300, and 509 K. Both OH+ and OD+ were produced. The rate constants were found to equal 1.2×10−9 cm3 s−1, independent of temperature or 〈KEcm〉. The branching into OH+ was observed to increase with 〈KEcm〉. Differences in the branching fractions were seen at a particular 〈KEcm〉 at different temperatures. These differences are attributed to a rotational temperature dependence such that increasing rotational temperature decreases the fraction of OH+ produced. The data are in agreement with a theoretical calculation and previous measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461291
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  • 9
    Electronic Resource
    Electronic Resource
    Evidence for an influence of rotational energy on the rate constants for the reaction of Ar+(2P3/2) with N2 (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 4761-4765 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Rate constants for the charge transfer reaction of Ar+(2P3/2) with N2 were measured as a function of average center-of-mass kinetic energy (〈KEcm〉) at three temperatures. The rate constants increase rapidly with (〈KEcm〉) at all temperatures. The thermal activation energy is derived to be 0.07 eV, which is approximately the value of the endothermicity of the reaction when N+2 (v=1) is produced. The rate constants vary with temperature at a particular 〈KEcm〉, indicating either an effect due to differing energy distributions in the drift tube at different temperatures or that the reactivity depends on the rotational temperature of N2. Comparing the data at constant average total energy indicates that translational and rotational energy have a similar effect on the reactivity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458666
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  • 10
    Electronic Resource
    Electronic Resource
    Kinetic energy, temperature, and derived rotational temperature dependences for the reactions of Kr+(2P3/2) and Ar+ with HCl (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 1149-1157 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Rate constants for the reactions of Kr+(2P3/2) with HCl and DCl and of Ar+ with HCl have been measured as a function of reactant ion/reactant neutral average center-of-mass kinetic energy (〈KEc.m.〉 ) at several temperatures. The measurements were made using helium as the carrier gas. From these data we have derived the dependences of the rate constants on the rotational temperature of H(D)Cl. Rate constants for the reaction of Kr+(2P1/2) with HCl have also been measured as a function of temperature. The rate constants for all of the reactions were found to decrease with increasing temperature. The rate constants were also found to decrease with increasing 〈KEc.m.〉 at low 〈KEc.m.〉 but then to increase at higher 〈KEc.m.〉 . A significant rotational temperature dependence of the rate constant was derived for the reaction of Kr+(2P3/2) with H(D)Cl. The analogous derivation for Ar+ reacting with HCl showed the rate constant for this reaction to be independent of the rotational temperature of HCl within experimental uncertainty.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459178
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