- Rate constants and branching fractions for xenon halide formation from Xe(3P2) and Xe(3P1) reactions
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The rate constants for XeF(B,C ), XeCl(B,C ), and XeI(B,C ) formation from reactions of Xe(3P1) and Xe(3P2) with NF3, NZF4, NF2, CCl4, and CF3I have been measured relative to XeCl(B,C ) formation from the reacti
- Lin, Daimay,Yu, Y. C.,Setser, D. W.
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- State-to-state relaxation processes for XeCl(B,C)
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The XeCl(B-X) and (C-A) emission spectra obtained from reaction of Xe(3P2 or 3P1) with Cl2, CCl4, and COCl2 in the presence of He, Ne, Ar, Kr, and N2 bath gases were used to study the vibrational relaxation and transfer between the B and C states of XeCl.By using the different Cl donors, different ranges of vibrational energy were emphasized.The bound-free emission spectra were simulated for various pressures of bath gas to obtain vibrational distributions.Numerical modeling of the XeCl(B) and XeCl(C) vibrational populations and the B/C intensity ratio as a function of pressure gave rate constants for vibrational relaxation and transfer, as well as the model for the state-to-state processes.For Ar as the bath gas, vibrational relaxation can be characterized by an exponential gap model Pij e-0.1ΔE/kT, with rate constants of (1-6), (6-12), and (20-30)x10-11 cm3 molecule-1 sec-1 for the v ranges of 0-30, 30-70, and 70-130, respectively.The rate constants for electronic state transfer are (3-11), (11-15), and (15-15)x10-11 cm3 molecule-1 sec-1 for the same v ranges.The vibrational energy loss upon electronic state transfer was best described by a Poisson-type function displaced to lower energy from the initial energy.These basic models also describe the relaxation in the other gases with He and Ne being less efficient and Kr and N2 more efficient than Ar.The magnitudes of the rate constants and the models are discussed.
- Dreiling, T. D.,Setser, D. W.
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- Xe(3P2)+HCL(v=1): Vibrational enhancement of XeCl* formation
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Formation of XeCl* from the Xe+(3P2)+HCl is slightly endothermic.In this work laser excitation of HCl (υ=1) in the presence of Xe(3P2 produuced in a flowing afterglow apparatus allows direct observation of XeCl* fluorescence from the Xe(3P2)+HCl(υ=1) reaction.The formation rate constant is determined to have a lower limit of 2*10-10 cm3 s-1.
- Chang, R. S. F.
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- Translational Energy Dependence of Reaction Dynamics in Kinematically Constrained Systems. Xe(3P2) + HCl, HBr, HI and CH3I
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The fully dispersed chemiluminescence spectra excited by reactions of Xe(3P2) with HI, HBr, HCl and CH3I have been recorded under superthermal beam-Maxwellian gas conditions.Direct spectral inversion has enabled determination of the rare-gas halide product vibrational energy distributions at selected collision energies in the range T> ca. (4-90)kJ mol-1.The mean vibrational energy disposals v> are found to increase linearly with the mean collision energy T>.This result, together with earlier measurements of reactive excitation functions (K.M.Johnson, J.P.Simons, P.A.Smith, C.Washington and A.Kvaran, Mol.Phys., 1986, 57, 255) and with the kinematic constraint on the dynamics, allows separate estimates of the mean energy disposals into rotation and translation, as well as the mean reactive cross-section.
- Hartree, William S.,Simons, John P.
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- Energy disposal in the two-photon laser-assisted reaction in xenon and chlorine gas mixtures
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The two-photon laser assisted reaction in a low pressure xenon and chlorine gas mixtures is studied to characterize the role of the entrance channel in determining the vibrational state distribution. A high degree of vibrational excitation in the XeCl product is measured. The measurements are in contrast with the vibrationally cold excimer observed following laser excitation in molecular beam experiments. The mean vibrational energy in the XeCl excimer depends upon the laser wavelength. As the laser is tuned toward shorter wavelength, an increasing fraction of the available energy from the reaction is observed.
- Kohel,Keto
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- Vibrational energy and bimolecular reactions: Enhancement of the electron transfer derived product channels for quenching of Xe(3P2) and Kr(3P2) atoms by CFnCl4-n, C2FnCl6-n
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The yields of XeCl(B,C) and KrCl(B,C) from the reactions of Xe(3P2) and Kr(3P2) metastable atoms with chlorofluoromethanes and chlorofluoroethanes are enhanced by the addition of vibrational energy to the molecu
- Sobczynski, R.,Setser, D. W.,Slagle, A. R.
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- Reactive quenching of two-photon excited xenon atoms by Cl2
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Total binary and tertiary quench rates have been measured for the reaction Xe (5p5np, np', n = 6,7) + Cl2 at thermal temperatures.Xenon atoms are excited by state-selective, two-photon absorption with an ultraviolet laser.The time-dependent fluorescence from the excited atom in the infrared, visible, and from XeCl* (B) product near 308 nm have been measured with subnanosecond time resolution.The decay rates are measured as a function of Cl2 pressure to 20 Torr and Xe pressure to 400 Torr.The measured reaction rates (k2 ca. 10-9 cm3 s-1) are consistent with a harpoon model described in a separate paper.We also measure large termolecular reaction rates for collisions with xenon atoms (k3 ca. 10-28 cm6 s-1).Total product fluorescence has been examined using a gated optical multichannel analyzer.We measure unit branching fractions for high vibrational levels of XeCl* (B) with very little C state fluorescence observed.
- Bruce, M. R.,Layne, W. B.,Meyer, Enno,Keto, J. W.
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- Spin-orbit state selective formation of rare gas chlorides from three-body ionic-recombination reactions of Rg+ (2P1/2,3/2) + Cl- + He at thermal energy
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The ArCl(C-A), KrCl(B-X,C-A,D-X), and XeCl(B-X,C-A,D-X) emissions have been observed from ionic-recombination reactions of Rg+ (Rg = Ar, Kr, or Xe) with Cl- in the flowing afterglow.Positive Rg+ ions are formed by He(23S)/Rg Penning ionization, while negative Cl- ions are produced through thermal electron attachment to CCl4.The dependence of RgCl* emissions intensities on the buffer He gas pressure indicates that the excimer emission arise from three-body reactions of Rg+ + Cl- + He.The spin-orbit state selectivity in the KrCl* and XeCl* formation is studied by isolating one of the spin-orbit levels of Rg+, 2P1/2 or 2P3/2.Although the Kr+ (2P1/2) reaction provides the KrCl(B-X,C-A,D-X) emissions with B:C:D distribution of 0.19 +/- 0.02:0.12 +/- 0.01:0.69 +/- 0.04, only XeCl(D-X)emission is observed from the Xe+ (2P1/2) reaction.The Kr+ (2P3/2) and Xe+ (2P3/2) reactions give the RgCl(B-X,C-A) emission with B:C branching ratios of 0.60 +/- 0.06:0.40 +/- 0.04 for KrCl* and 0.62 +/- 0.06:0.38 +/- 0.04 for XeCl*.The high propensities for the D formation from the Rg+ (2P1/2) reactions and for the B and C formation from the Rg+ (2P3/2) reactions suggest that Rg+ (2P1/2) + Cl- and Rg+ (2P3/2) + Cl- characters are conserved well for the formation of RgCl* in the three-body ionic-recombination reactions.The relative formation rate of RgCl(D) from the Rg+ (2P1/2) reaction to that of RgCl(B,C) from the Rg+ (2P3/2) reaction was estimated to be 0.14 +/- 0.02 for KrCl* and 0.033 +/- 0.006 for XeCl*.The slower RgCl(D) formation rates are attributed to fast predissociation of + (2P1/2)Cl-> intermediates into Rg* + Cl and/or Rg + Cl than that of + (2P3/2)Cl->* ones.
- Tsuji, Masaharu,Furusawa, Makoto,Kuono, Hiroyuki,Nishimura, Yukio
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- Comparison of the Rg+(2P1/2)/Cl-/He and Rg+(2P3/2)/Cl-/He three-body ionic-recombination reactions for the formation of RgCl*, Rg*, and Cl*<
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Three-body ionic-recombination reactions of Rg+ + Cl- + He (Rg = Kr or Xe) leading to RgCl* excimers and their predissociation products (Rg* and Cl*) have been studied by observing emission spectra in
- Tsuji, Masaharu,Muraoka, Toshihiko,Kouno, Hiroyuki,Nishimura, Yukio
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- XeF* and XeCl* Formation in Low-Pressure Tesla Coil Discharges
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The XeCl* and XeF* emission spectra have been studied from mixtures of Xe with HCl, Cl2, CCl4, NF3, BF3, C2F6, and SF6 in a tesla-coil-driven discharge.The XeX* emission spectra were recorded at pressures below 0.75 torr for all reagents except BF3, and C2F6, which did not give XeF* emission.Low-pressure pulsed dc discharge experiments in Xe/Cl2 and Xe/HCl mixtures gave XeCl* emission spectra very similar to those observed from the tesla-driven discharge.Computer simulations of the XeCl(B-X) spectra from discharges of Xe with Cl2, CCl4, and HCl provide an estimate for the XeCl(B) vibrational distributions.Since Xe(3P2) and Xe(3P1) reacting with HCl and SF6 do not give XeX*, the observation of XeX* from these two reagents requires the reactions of Xe Rydberg states or recombination of Xe+ and Cl- or F- ions.Arguments based upon XeCl* and XeF* vibrational and electronic state populations and the time dependence of the emission suggest that Rydberg state reactions are the dominant mechanism contributing to the XeX* excitation from the low-pressure discharge of Xe/HCl and Xe/SF6 mixtures.
- Wren, D. J.,Setser, D. W.,Ku, J. K.
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- Nonresonant collision-induced absorption in Xe/Cl2 mixtures
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Mixtures of Xe and Cl2 have been irradiated at 193 nm with a pulsed ArF laser.The collision-assisted laser-induced absorption results in emission of XeCl (B and C) at 308 and 340 nm, respectively.The intensity of XeCl emission is found to vary linearly with ArF laser power, indicating the occurrence of a single photon-assisted collision-induced process.The temporal characteristics of the emission vary substantially with the number density of each reagent showing fast formation and decay rates at high densities, but slower rates at lower densities.A kinetic mechanism is proposed in which a (XeCl2)* trsnsient complex is initially formed and that complex subsequently dissociates to yield XeCl*.
- Wilcomb, B. E.,Burnham, R.
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- Decay kinetics of XeCl (B,C) in Xe and in mixtures of Xe with Kr, Ar, Ne, and He
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The two-photon, laser-assisted reaction between Xe and Cl2 has been used to prepare XeCl (B,C) molecules in Xe and in Xe mixtures with lighter rare gases for kinetic studies of the coupled XeCl (B,C) states.The XeCl (B-X) spectra were used to assign the conditions for which the vibrational temperature was nearly 300 K.Relative intensity and coupled radiative lifetime measurements provide independent data which support an energy separation between the XeCl (B) and XeCl (C) states of ca. 100 cm-1.The two-body quenching rate constant in Xe for XeCl (B,C) was measuredas 5+3-2x10-12 cm3 s-1, and a three-body quenching rate constant of 13 +/- 4x10-31 cm6 s-1 is indicated.Experiments also were done with added Kr, Ar, Ne, and He to establish two-body and mixed (e.g., Xe + Ar) three-body quenching rate constants.The three-body quenching rate constants are nearly equal to the Xe2Cl* formation rate constants and three-body dark quenching of XeCl (B,C) is negligible.
- Quinones, E.,Yu, Y. C.,Setser, D. W.,Lo, G.
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- The theoretical and experimental distinguishing of photoassociation intothe XeCl(B) state
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The spectrum of excitation into the XeCl(B) state is simulated by a procedure rigorously taking into account the bound-bound (bb) and free-bound(fb) transition contributions. The cross-sections for bb-absorption and photoassociation are calculated, and at their maxima, near λ=308 nm, they amount to 1.2E-16 cm**2 and 1.4E-38 cm**5, respectively. An ex perimental approach is developed enabling the distinguishing of fb-transition contributions by monitoring the excitation into the XeCl(B) state in conditions when the equilibrium between nonexcited XeCl(X) molecules and free Xe and Cl atoms does not have time to be completed. The experimentally obtained ratio of intensities for the bb- and fb-transitions, amounting to 1.8-3.3, is in good agreement with the calculations. These experiments enabled estimation of the rate constant for XeCl(X) state dissociation in bimolecular collisions with Xe atoms as being (3-6)E-11 cm**3 s**-1.
- Gordon, E. B.,Egorov, V. G.,Nalivaiko, S. E.,Pavlenko, V. S.,Rzhevsky, O. S.
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- Infrared Chemiluminescence Studies of the H + NFCl2 and H + NFCl Reactions
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The primary and secondary reactions in the H + NFCl2 system have been studied by infrared chemiluminescence in a fast flow reactor at 300 K.The primary reaction is exclusively Cl atom abstraction to give HCl(ν=0-4) + NFCl with a total rate constant of (1.9 +/- 0.4) X 10-11 cm3 molecule-1 s-1 and an inverted vibrational distribution of Ρo-Ρ4 = 9:20:32:27:12.The rate constant for HF formation from H + NFCl was estimated as (0.9 +/- 0.4) X 10-11 cm3 molecule-1 s-1, and the HF vibrational distribution, Ρo-Ρ3 = 42:34:18:6, is characteristic of unimolecular HF elimination reactions.These data for the HF + NCl(a) product channel from the H + NFCl reaction are compared to earlier studies, which provided information about the HCl + NF(a) product channel.The latter seems to be the more important, and the total rate constant for H + NFCl is about 4 X 10-11 cm3 molecule-1 s-1 at 300 K.The dynamics of the H + NFCl reaction are discussed and compared to the H + NF2 reaction.A small number of experiments also were done with the H + NF2Cl reaction system.
- Arunan, E.,Liu, C. P.,Setser, D. W.,Gilbert, J. V.,Coombe, R. D.
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p. 494 - 501
(2007/10/02)
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- Two-Photon Direct Laser-Assisted Reaction between Xe and ClF
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The two-photon laser-assisted reaction between Xe and ClF under dilute gas conditions is demonstrated.The only product is XeCl(B,C) in contradistinction to the reactions of Xe(6s) and Xe(6p) atoms with ClF or the reaction of ClF(4s1,3Π) with Xe, which give both XeCl(B,C) and XeF(B,C).The excitation spectra from the laser-assisted reaction Xe/ClF and Xe/Cl2 are compared.Arguments based upon product-state distributions and the laser intensity dependence are summarized to favor a direct, rather than a stepwise, mechanism for the laser-assisted reactions of Xe with halogens under dilute gas conditions.
- Qin, J.,Nelson, T. O.,Setser, D. W.
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p. 5374 - 5378
(2007/10/02)
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- Ion Recombination Rates in Rare-Gas Cation-Halide Anion Systems. 2. KrF* and XeCl*
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The emission spectroscopy/pulse radiolysis method of determining three-body ionic recombination rate constants in rare-gas-halogen source gas mixtures has been extended to systems where the emission is produced by both ionic and nonionic pathways.This has enabled recombination coefficient measurements to be done over a large pressure range for irradiated Kr/SF6 and Xe/CFCl3 gas mixtures.The rate constants measured for both these systems show the typical pressure dependence of an increase to a maximum value of ca. 2.5E15 M-1 s-1 (ca. 4E-6 cm3 s-2), before the onset of the diffusion-controlled reaction.These values have been compared to the predictions of the Langevin-Harper diffusion-controlled and the Bates termolecular recombination models.The large discrepancies between theory and experiment have shown that other recombination processes dominate the ionic recombination.
- Mezyk, Stephen P.,Cooper, Ronald,Sherwell, John
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p. 3152 - 3158
(2007/10/02)
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- Interpretations of XeI and XeBr bound-free emission spectra and reactive quenching of Xe(3P2) atoms by bromine and iodine containing molecules
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The XeBr and XeI emissions spectra have been recorded in a flowing afterglow apparatus from the reaction of Xe(3P2) atoms with 16 bromine and iodine containing reagent.In all cases both the B and C states of XeI and XeBr are observed; the initial B/C ratio is ca. 1.5.The ratio increase with pressure because of collisional transfer from C to B.Comparison of the total XeBr and XeI emission intensities with the XeCl emission intensity from Xe(3P2) + Cl2 is used to obtain rate constants for XeBr and XeI formation.The branching fractions for XeI and XeBr formation are large, probably unity, for Br2, I2, ICl, and IBr and relatively small for the polyatomic molecules except for CF3I and possible CBr4.From the short wavelength limit of the B-X spectra, upper limits to D0(R-Br) and D0(R-I) are assigned.The theoretical potential curves calculated by Dunning and Hay for the A, B, C, and X states of XeI and XeBr were slightly adjusted so that good agreement was obtained between the simulated and experimental spectra from low vibrational levels of the B and C states.These adjusted potential curves were used to simulate the spectra from high levels of XeBr and XeI, and initial XeBr and XeI vibrational distributions were assigned from matching the low pressure spectra.A systematic decrease in V(XeX)> is observed in the Cl2, Br2, I2 series and interpreted as evidence for X(2P1/2) formation.The XeBr and XeI vibrational energy disposal is compared to that from reactions of metal atoms with halogen donors and with reactions of Xe(3P2) with chlorine and fluorine donors.
- Tamagake, K.,Setser, D. W.,Kolts, J. H.
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p. 4286 - 4305
(2007/10/02)
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- Emission spectra of KrXeCl*, KrXeBr*, KrXeI*, ArKrF*, and ArKrCl*
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Sensitized reactions of Xe and Kr with halogen donors in the presence of high buffer gas pressures of Kr and Ar, respectively, have led to the observation of five emission bands in the ultraviolet region of the spectrum.These broad structureless bands are assigned to the mixed rare gas-halide trimers KrXeCl*, KrXeBr*, KrXeI*, ArKrF*, and ArKrCl*.Despite an extensive search, no emission corresponding to KrXeF* could be found and this mixed trimer may be unstable because of interaction with a lower repulsive state.The positions and half-widths of the five emission bands are characterized, and the formation mechanism of the mixed trimers in these experiments is discussed.
- Brashears, H.C.,Setser, D.W.,Yu, Y.-C.
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