15861-05-9Relevant articles and documents
Temperature-dependent quenching rate constants of NF(a1Δ)
Manke II, Gerald C.,Henshaw, Thomas L.,Madden, Timothy J.,Hager, Gordon D.
, p. 1708 - 1714 (2007/10/03)
The temperature dependence of the rate constants for NF(a1Δ) quenching by Cl2, HCl, O2, and CO over the temperature range 300-480 K have been measured in a flow reactor. The rate constant data were fit by Arrhenius expressions k(T, Cl2) = 1.6 ± 1.0 × 10-11 exp(-1100 ±250/7), k(T, HCl) = 2.0 ± 1.0 × 10-10 exp(-3270 ± 250/7), k(T, O2) = 1.5 ± 0.5 × 10-14 exp(-300 ± 150/7) and k(T, CO) = 2.0 ± 1.0 × 10-12 exp(-2000 ± 250/7), cm3 molecules-1 s-1. Reaction mechanisms and possible products are discussed for each reaction.
Generation of NBr(a1Δ) by the reaction of N3 radicals with Br atoms: A flow reactor source for quenching rate constant measurements
Hewett, Kevin B.,Setser
, p. 335 - 342 (2008/10/08)
The reaction between azide radicals (N3) and Br atoms is shown to produce electronically excited NBr(a1Δ) molecules in a room temperature flow reactor. This chemical system provides adequate concentration of NBr(a1Δ) so that this molecule can be systematically studied. The yield of NBr(b1Σ+) is minor. The quenching reactions of NBr(a) with HCl, HBr, HI, NH3, Br2, CF2Br2, and O2 were examined; the rate constants are (22 ± 5) × 10-14, (280 ± 30) × 10-14, (2300 ± 200) × 10-14, (35 ± 3) × 10-14, (2600 ± 300) × 10-14, (37 ± 6) × 10-14, and (230 ± 30) × 10-14 cm3 molecule-1 s-1, respectively.
The microwave spectrum of the NF radical in the second electronically excited (b 1Σ+) state: Potentials of three low-lying states (X3Σ-, a 1A, b1Σ+)
Kobayashi, Kaori,Saito, Shuji
, p. 6606 - 6610 (2007/10/03)
The pure rotational transition of the NF radical in the second electronically excited state, b 1Σ+, was detected by microwave spectroscopy. The NF radical was generated by dc-discharge through a mixture of NF3 and H2 at around 90 K. Six rotational transitions for v= 0 and four for v = 1 were observed in the 73-442 GHz region. In addition to the rotational and centrifugal distortion constants, the quadrupole coupling constant of the nitrogen nucleus of NF(b 1Σ+) was determined for the first time from the lowest two transitions of NF in the v = 0 level. The spectrum of NF(a 1Δ) in the first vibrational excited state was also observed in order to derive highly accurate potential parameters for comparison with the data of NF(X 3Σ-,b 1Σ+).
Line strengths of diatomics: The b 1Σ+v′=0→X 3Σ-v″=0 transition of the NF radical
Di Stefano,Lenzi,Piciacchia,Ricci
, p. 2752 - 2759 (2007/10/03)
Line intensities in the (0,0) band of NF(b 1Σ+→X 3Sigma;-) spin forbidden emission have been observed in a microwave apparatus. Deduced line strengths of the OP and SR well resolved branches are shown differently, in contrast with the theoretical prevision, and are interpreted by taking into account some peculiarities of the NF radical. An intermediate (a) and (b) Hund case is seen to apply to OP and SR in the whole rotational range examined. Accordingly, a reliable value for the effective transition moment μe is evaluated from the experiment.
Infrared Chemiluminescence Studies of the H + NFCl2 and H + NFCl Reactions
Arunan, E.,Liu, C. P.,Setser, D. W.,Gilbert, J. V.,Coombe, R. D.
, p. 494 - 501 (2007/10/02)
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.
Rates of Reactions of N3 with F, Cl, Br, and H Atoms
Liu, X.,MacDonald, M. A.,Coombe, R. D.
, p. 4907 - 4912 (2007/10/02)
The room temperature rate constant of the reaction F + N3 -> NF + N2 has been determined by monitoring the time dependence of laser-induced fluorescence from the intermediate N3 radicals in the presence of a large excess of F atoms.Experiments were performed with CF4, SF6, and F2 as precursors of the F atoms.The results indicate that the F + N3 rate constant is (5.8 +/- 0.6) x 10-11 cm3 s-1 at 298 K.Rate constants for the reactions of N3 with H, Cl, and Br atoms were determined from competitive rate studies in which N3 was allowed to react with mixtures of each of these atoms with F atoms.The data indicate rate constants of (1.0 +/- 0.1) x 10-10, (2.8 +/- 0.4) x 10-10, and (3 +/- 2) x 10-10 cm3 s-1 for H + N3, Cl + N3, and Br + N3, respectively.
A Coefficients of the a1Δ States of NF and NH
Bradburn, Gregory R.,Lilenfeld, Harvey V.
, p. 555 - 558 (2007/10/02)
The Einstein A coefficients of the paramagnetic species NF (a1Δ) and NH(a1Δ) have been measured in the gas phase.The excited states were detected by both optical emission spectroscopy and electron paramagnetic resonance (EPR) spectroscopy.The optical detection systems were calibrated using luminescence from the emission of either the air afterglow reaction or O2(a1Δ).The Einstein A coefficient of NF(a1Δ) was determined to be 0.15 (+/-0.04) s-1, in good agreement with a previous measurement.This work is believed to be the first experimental determination of the gas-phase Einstein A coefficient of NH(a1).Our value for this A coefficient is 3.7(+/-0.6)s-1.In addition, we believe that this is the first report of the detection of NH(a1Δ) in the gas phase using EPR.
Kinetics and Mechanism of the Reaction of NFCl2 with Hydrogen Atoms
Exton, D. B.,Gilbert, J. V.,Coombe, R. D.
, p. 7758 - 7762 (2007/10/02)
The reaction of gaseous NFCl2 with excess H atoms has been observed in a continuous flow reactor.The reaction produces excited singlet states (a1Δ, b1Σ+) of NF and NCl and is thougth to proceed by a two-step mechanism in which H atoms react with NFCl2 to produce primarily HCl and NFCl, followed by the H + NFCl reaction which proceeds to both HCl + NF and HF + NCl.The rate constant of the first step, H + NFCl2, is (2.6 +/- 0.2) * 10-12 cm3 s-1 at 298 K.The rate constant of the second step, H + NFCl, was too great to be accurately measured with our apparatus.Overall, the two-step process shows a roughly 10-fold preference for the production of NF(a1Δ) over NCl(a1Δ).The generation of both NF(a1Δ) and NCl(a1Δ) in this system results in energy pooling among these species which produces NF(b1Σ+).This process is significantly enhanced by the admission of HI to the reaction medium.
Production of NCl(a) by Thermal Decomposition of ClN3
Benard, D. J.,Chowdhury, M. A.,Winker, B. K.,Seder, T. A.,Michels, H. H.
, p. 7507 - 7514 (2007/10/02)
Thermal decomposition of ClN3 by pulsed CO2 laser pyrolysis has been investigated by using SF6 as a sensitizer.The electronically excited decomposition products, NCl(a) and NCl(b), were monitored by absolute time-resolved emission spectroscopy while ClN3 was followed by ultraviolet absorption.The results indicate a higher barrier to dissociation of ClN3 than FN3, consistent with ab initio calculations, and an NCl(a) yield of order unity, based on a nominal 0.7/s radiative rate for the NCl(a-X) transition.Studies of simultaneous dissociation of FN3 and ClN3 have also revealed that NCl(a), when coproduced with NF(a), upconverts the latter species to NF(b) efficiently (in the presence pf trace I2) and cooperatively pumps the IF(B) state (upon addition of CF3I) by an energy pooling mechanism that does not involve NF(b) as an intermediate.These results indicate a potential for development of chemical lasers that operate on either the NF(b->X) or IF(B->X) transitions at visible wavelength.
Quenching Rate Constants of NF(a1Δ) at Room Temperature
Du, Kang Yan,Setser, D. W.
, p. 2425 - 2435 (2007/10/02)
The gas-phase quenching rate constants for NF(a1Δ) have been measured at 300 K for 60 reagent molecules.The experiments were done in a Pyrex glass flow reactor coated with halocarbon was using the 2F + HN3 reaction as a source of ND (a1Δ).The rate constants span a wide range of values; the rate constants for most diatomic molecules are less than 1E-14 cm3 molecule-1 s-1, but more reactive molecules, such as C2H4, NH3, or P(CH3)3, have rate constants near 1E-11 cm3 moleczule-1 s-1.For polyatomic reagents that can act as Lewis bases, a correlation was found between the magnitude of the quenching rate constant and the base strength (measured as the proton affinity) of the molecule, which is evidence that the closed-shell (?x2-?y2) component of the NF(a1Δ) state is involved in the quenching.The rate constants NF(a1Δ) are larger than for the analogous O2(a1Δ) state because of the more attractive interaction potentials between NF(a) and stable reagent molecules.A few experiments were done at ca. 200 K to demonstrate that this NF(a) source is suitable for low-temperature studies; the rate constants for O2, CO and C2H4 decreased with reduction in temperature.The 300 K bimolecular self-removal rate constant for NF(a1Δ) was assigned as (5 +/- 2) * 1E-12 cm3 molecule-1 s-1; bimolecular energy pooling by NF(a) to give NF(b) is not an important quenching pathway.Quenching of NF(a) by F atoms has a small rate constant, (4 +/- 2) * 1E-13 cm3 s-1.
